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Trailer Light Mounting Bracket for 4" Trailer Lights, Steel - Black Powder Coat

Trailer Light Mounting Bracket for 4" Trailer Lights, Steel - Black Powder Coat

Item # BK45BB
Our Price: $7.17
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Shipping Weight: 0.59 lbs
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6" L x 5-13/16" W with 1-3/8" base; Powder coated steel; mount vertical or horizontal; requires A45GB grommet; mounts on 4" centers 1-800-940-8924 to order Optronics accessories and parts part number BK45BB or order online at Free expert support on all Optronics products. Great prices and Fastest Shipping for Trailer Light Mounting Bracket for 4" Trailer Lights, Steel - Black Powder Coat. Accessories and Parts reviews from real customers.
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Optronics Accessories and Parts - BK45BB

  • Trailer Lights
  • Mounting Hardware
  • Brackets
  • Optronics
  • 4 Inch Diameter
  • Black

6" L x 5-13/16" W with 1-3/8" base; Powder coated steel; mount vertical or horizontal; requires A45GB grommet; mounts on 4" centers

Trailer Light Mounting Bracket for 4" Round Lights, Steel - Black Powder Coat

A black, steel bracket for mounting 4" round lights. The bracket measures 6" long x 5-13/16" wide with a 1-3/8" deep mounting base. The bracket has a 4-1/2" wide hole in the center for mounting the light, and has six screw holes in the bracket spaced equally around the hole. The black powder coated bracket is made from sturdy, durable steel and can be used to mount lights vertically or horizontally. The bracket base mounts on 4" centers. Along with the sealed light, the A45GB grommet is required to complete the installation.

  • Black, powder coated bracket for mounting 4" round lights
  • Constructed from strong, durable steel
  • Mounts lights vertically or horizontally
  • Lights mount into 4-1/2" hole in center of bracket with 6 surrounding screw holes
  • Base mounts on 4" centers
  • Dimensions: 6" L x 5-13/16" W with 1-3/8" deep base
  • Requires grommet A45GB to complete installation

Manufacturer Specifications

Black powder coated steel bracket for horizontal or vertical mounting on 4" round lights. A45GB grommet required for complete installation.

dimensions of light

BK45BB Black Bracket for 45 Series, Powder Coated by Optronics, Inc.

Alternate part number: BK-45BB

California residents: click here

Customer Reviews

Trailer Light Mounting Bracket for 4" Trailer Lights, Steel - Black Powder Coat - BK45BB

Average Customer Rating:  4.9 out of 5 stars   (48 Customer Reviews)

6" L x 5-13/16" W with 1-3/8" base; Powder coated steel; mount vertical or horizontal; requires A45GB grommet; mounts on 4" centers


The part was as expected. Good delivery time. The only very minor complaint is the notification that the part had shipped. It got here when it was supposed to but I did not know for sure it was coming until two days after shipping and the day before delivery.
These folks have always done a great job with customer service in the last 10 or so years I have been buying from them.

John M.


Just fine


Brackets are ok, but whoever made them skipped 30 seconds of prep work by not cleaning up the edges of the bracket. Cut my hand multiple times while installing the taillight into the bracket. Simply some quick sanding or some wire wheel work would have solved this. No point in doing it now as it would damage the powder coating. Mildly annoyed, but still decent product for the price.



After a year of use they are still holding up. Powder coating is resisting the elements well. Im still satisfied with the purchase. Despite the issues I had with the manufactures product prep did not effect the performance of the part. Would by again if needed.


Here's installed photos...

Nick L.




I bought Brackets, Rubber grommets, Sealed round ( ST45RB ) lights and wire ends plugs. I also bought 4 other bulb lights. The sealed round lights don't fit tight in the rubber grommet, the light has a loose fit and the light turns in the grommet. One of the sealed lights only lasted 2 weeks and it went out.


I buy many products from Etrailer -- Very high quality merchandise - exactly what I need for my business- super service- fast delivery time - I always get what I expect- I have told other people where I get my trailer stuff ----- I have a golf cart repair business and wire trailers--- (excellent rating) --- Dale A.


I purchase some 4" round LED tail lights with grommets and was trying to find a way to mount them. Then I found this mounting bracket on and ordered 4 of them. I have just received them and they work perfectly with the 4" round LED tail lights. Thanks etrailer.
Troy D Smith


Bracket was very affordable. I was somewhat concerned that it might be flimsy or too light to protect the LED light I wanted to use. But the bracket is well painted, the hole selection matches perfectly with the three holes in the light rim. The bracket is very solid and an excellent weight to last. You will like this bracket if you need to mount a 4 1/2 inch tail/stop/turn light.


Works perfectly with the round LED lights (product STL42RB in my case).


Got these for my car trailer. Was originally going to cut mine out out of plate steel but these were to cheap not to get. They are very strong with good thick metal. Going to weld them on instead of bolting but either way, I think they would be plenty strong. Great product, well worth it.


Converting an older home made trailer to LED lighting. These high quality parts worked great. Received order within 3 days. Thanks


Good sturdy mount. Only problem is they will start rusting after a season or two if you use them in salt water. I wish they made them with a galvanized finish or out of Stainless steel


Bracket look great and fit my lights perfectly. Once I get them mounting I think they will look great as well.


Not a lot to say about the product, it's pretty simple and does everything it's supposed to do. What was remarkable was the help I received from etrailer finding the product and the speed at which it was delivered to me. I am a happy customer.


The bracket is excellent quality. Heavy duty construction and fit the light assemblies and grommet perfectly. The shipping was extremely quick, and the price just right. Would recommend highly.


Brackets are extremely solid and well built, I am confident they will last a very long time. Because of their durability I was not able to bend them to the angle I wanted but I was able to relocate them to a new position on the trailer.


Lights fit right into brackets


Good product good service
I like
ordering from E trailer


Great looking product, can't wait to install and see how they look. Thanks etrailer for fast service


Great product ... Exactly what I needed!
Thanks !

Barry H.


Super Product .... Very Pleased !


great looking bracket should work just fine.


These brackets are exactly what I neede d.


fast shipping very happy look good on my old trailer


did what i wanted



does its job


Item is exactly as described. High quality,
duty material. This was a smooth
Transaction, shipping was fast, price was good and I will
Definitely do business here again.
Thanks again


Great strong bracket made out of quality metal and comes prepainted that isn’t easy to scratch.

Show More Reviews

See what our Experts say about this Optronics Accessories and Parts

  • What Size are the Mounting Holes for the Trailer Light Mounting Bracket # BK45BB
    I went out to the warehouse and measured the mounting holes for the trailer light mounting bracket # BK45BB. The larger holes on top are 0.36 inches in diameter so 5/16 inch hardware would be the largest you could use. The smaller holes on the face of the bracket will accept up to 1/8 inch hardware. I also made a video showing the measurement of the large holes using digital calipers.
    view full answer...
  • Trailer Light Mounting Bracket
    The mounting bracket in the picture you submitted looks very similar to # BK45BB. This bracket is for a 4-1/2 inch round trailer light and is 6 inches long, 5-13/16 inches wide and 1-3/8 inches deep. The base mounting holes are spaced 4 inches apart.
    view full answer...
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  • How Thick Of a Plate Will the Optronics Rubber Grommet for 4 Inch Round Lights Fit
    I went out to our warehouse to measure the seat of the # A45GB grommet that you referenced. It seems like it will be a tight fit for your 3/8 inch bumper. The grommet seat measures 0.24 inches. Another option for mounting a 4 inch round light on your trailer, instead of the bumper, is to use the Trailer Light Mounting Bracket # BK45BB. This may not work for your application, but it could also be modified to work how you need. This bracket will work well with the rubber grommet # A45GB.
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  • Best Suspension Enhancement for 2019 Nissan Titan XD Towing Trailer
    The best suspension enhancement for your 2019 Nissan Titan XD is the RoadActive Suspension Custom Leaf Spring Enhancement Kit # RAS3611 because it is an active system which works to continually reinforce your Nissan's original leaf spring suspension. The way it works is really simple but extremely effective: the force normally put on your truck's current springs - especially when towing but also when carrying cargo or when making a tight turn - gets transferred to the RAS Enhancement Kit,...
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  • How Does Trailer Light # ST45RB Mount into Mounting Bracket # BK45BB
    I went out to the warehouse and pulled Optronics Trailer Light, # ST45RB. First, you will need to place the Rubber Grommet, # A45GB, into the mounting bracket, # BK45BB. Next, you will need to press the light until it is seated all the way in the bracket. This last step actually takes some strength as the light is held in place by the grommet. I had to use some lubricate to get the light to seat all the way in the mounting bracket. Once in place, the light will not come out unless it is...
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  • Are there Replacement Tail Lights for a 1982 Scamp Trailer
    In order to determine which replacement lights will fit your 1982 Scamp trailer, you will need to find the manufacturer and model number of the light assembly. This could involve removal of the assembly. If you see numbers on the lens, those are not the correct numbers. If you cannot find any manufacturer/model number information, you will need to measure the diameter of your existing tail lights and any other dimension that you can. You will also need to determine how they mount to the...
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  • Could Use a Trailer Light Mounting Bracket with a Sealed 4 Inch LED Stop Light
    Yes, I went out into our warehouse and pulled a Sealed, 4 inch Round LED Trailer Stop # STL42RB and a Trailer Light Mounting Bracket # BK45BB and found that they work together very well. All of the mounting holes from the # STL42RB line up with the # BK45BB. You would need bolts that have a diameter of no more than 3/16 of an inch to attach the light to the bracket. I attached a picture to the right that shows how these products would look if installed together. You might also be interested...
    view full answer...
    Image 1 for
  • Can the 4 inch Rubber Grommet # A45GB be used in a 4-3/4 inch Mounting Location
    I do have a solution for you, since the hole that you are placing the grommet in is 4.75 inches, the grommet that you referenced, the Optronics # A45GB, might push through that mounting hole since the overall diameter is 5-3/8. Depending on your exact mounting location you might be able to use the # BK45BB to install on your light mounting location then use the 4 inch grommet # A45GB to hold a 4 inch light. I am not sure if this will work for your application but you might also be able...
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  • Wiring and Mount for Optronics 4 Inch Round Trailer Light # ST45RB
    Sealed, 4" Round Trailer Stop, Turn and Tail Light, Flush Mount, 3-Function Item # ST45RB has a plug in the back to accept pigtail # A45PB. On it the white wire is ground, black is for tail lights, and red is for brake lights and turn signals. This light can be mounted using grommet # A45GB with bracket # BK45BB. Or if mounting directly in a surface you would just need the grommet. I have linked videos of all of these parts for you.
    view full answer...
  • Replacement LED Trailer Tail Lights for a 2005 Gulfstream BT Cruiser
    Optronics trailer tail light # ST45RB is potentially a fit for your trailer if the existing lights are one of the following: Uni Bond # SE4000R Wesbar # 423541 Truck Lite # 40282R/40202R Grote # 52922 Peterson # 426R Bargman # 40-01-001 This information is likely on the light housing somewhere on your existing lights. The 2 knobs on the back are not an issue since this light would mount in a hole in the trailer or in mounting bracket # BK45BB both using grommet # A45GB. If you are not...
    view full answer...
  • Functions of Optronics 12 Diode Miro-Flex Tail Light # STL23RB
    The Optronics 12 Diode Miro-Flex LED Trailer Stop/Turn/Tail Light you referenced, part # STL23RB is a three function lamp. The # A47PB right angle pigtail, which is sold separately, has a white ground wire, a red wire that carries the brake and directional signal and a black wire that serves as the running light circuit. If the vehicle headlights were turned on, the lamp would be lit. Applying the brakes would make the lamp brighter. The lamp has several mounting options. It can be...
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  • Troubleshooting Light Not Working with the Cargo Carrier Light Kit # 52014
    If you installed the Cargo Carrier Light Kit # 52014, and all of the functions on one light are not working then it sounds like the problem is the light itself. If some of the functions worked on the light then I would say that you have a problem with the wiring somewhere. You can test the light by running a ground to the marked pin and then test the other 2 pins with a 12V power source. If you think that the wiring may be an issue then you can replace it with part # WHCETR1B. For a replacement...
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  • Installation Assistance With Mounting Hole Dimensions Optronics GLOLight LED Stop/Turn/Tail Light
    To install the Optronics GLOLight LED # STL101RMB you will also need grommet # A45GB. There are two mounting options for this LED light. The first one is using Optronics grommet # A45GB and mounting directly into your 1998 Jeep Wrangler. The other option is using the Optronics Mounting Bracket # BK45BB. If you decide to use the mounting bracket, you will still need the grommet as well. If you are mounting using the grommet only the grommet opening is 4-1/2 inches. When cutting this...
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  • Replacement Reverse Light for Ranger z521 Boat Trailer
    I have a solution that may work for you, but we do not currently have any 3" diameter submersible reverse lights. Have a look at the Optronics Backup Light # BU45CB which is a 4-1/4" diameter light that can be mounted to your trailer using mounting bracket # BK45BB. You will also need the 2 wire pigtail # A45CB to replace the wiring from your old lights and plugs into the back of this Optronics light. I've attached a photo that outlines the dimensions of the light to see if you can match...
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    Image 1 for Image 2 for
  • Optronics GLOLight LED Stop/Turn/Tail Light Availability
    We do carry the GLOLight # STL101RMB as well as several other GLOLight products. I have attached link for the GLOLight product page. This unit has a four inch diameter; for installation you will also need to order the following: Three-Wire Pigtail part # AL45PWTB; Rubber Grommet part # A45GB; and the Mounting Bracket part # BK45BB. I attached a short video of the GLOLight # STL101RB, which is the same base part as the one you reference, however, the video is demonstrating the part with...
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  • Weathertight Wiring Plug and Stainless Steel Bracket for 4 GloLight LED Trailer Tail Light
    There are 2 different possible connectors you can use for the wiring when it comes to the GloLight LED Trailer Tail Light # STL101RMB; the 3-Wire Pigtail # A45PMB which installs using splicing, and the Three-Wire Straight Pigtail # AL45PWTB which connects to the industry standard 3-way connector for lights. Please note that if you will be using the splicing method then you want to use heat shrink butt connectors like what comes with the kit # DW05743-10 as they will be much more effective. When...
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  • Availability of 2 Inch Diameter 3-Function Taillight
    There is not a 3 function lamp available that has a 2 inch diameter. DOT regulations require that tail lamps meet certain size and visibility requirements. Clearance/marker lights can be smaller, but a 2 inch diameter taillight would not meet those requirements. There is a 4 inch diameter lamp, part # ST45RB. The lamp would typically mount in a grommet like part # A45GB set into an existing hole or using a bracket like # BK45BB.
    view full answer...
  • Trailer Light And Mounting Bracket Recommendation
    The Optronics light, part # STL42RB, you are asking about uses the mounting holes in the included flange for mounting. This light features 10 Super LED lights and has a sealed, waterproof housing and lens kit. The mounting holes in the flange are spaced 4-1/4 inches apart center-to-center. We do have a mounting bracket, part # BK45BB, for a 4 inch light but the mounting holes are spaced 4 inches center-to-center. If you wished to drill the holes in the bracket to match the holes in the...
    view full answer...
  • Availability of Mounting Bracket for 2-1/2 Diameter Round Sealed Trailer Lights
    We do indeed have a bracket designed for 2-1/2 inch diameter trailer lights, part # BK55BB. You would also need the rubber grommet, part # A57GB. The bracket and grommet would work with a 2-1/2 inch diameter lamps like part # MC57RB or # MC57AB.
    view full answer...
  • Is Optronics LED Trailer Tail Light # STL42RB Sold Individually or In Pairs
    The Optronics LED Trailer Tail Light # STL42RB is sold individually. If you needed a pair you'd need to order a quantity of two of these. For a wiring harness you'd then need the part # A47PB and for a mounting bracket part # BK45BB and you'd be set.
    view full answer...
  • Replacing Trailer Tail Lights With LEDs on Older Trailer
    Thank you for that photo, it was helpful! For new LED lights you will need to replace the entire unit, and you will need to replace the entire unit. Based on the 2-1/4 inch measurement, to mount new LED tail lights you are going to have to drill new holes to install them because the standard for trailer lights today is 2 inches on center. I recommend the Trailer Tail Lights # TLL9RK.
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    Image 1 for
  • Which Trailer Tail Lights Work With 4" Trailer Light Mounting Bracket BK45BB
    I would be happy to help! The Trailer Light Mounting Bracket for 4" Trailer Lights, Steel - Black Powder Coat # BK45BB you were looking at works with 4" round lights so I recommend the Optronics LED Trailer Tail Light - Stop, Tail, Turn - Submersible - 21 Diodes - Round - Red Lens # STL55RB. You will also need Rubber Grommet # A45GB and Wiring Pigtail # A45PB. I recommend using heat shrink butt connectors # DW05744-5 for a weather tight connection. I included videos of the products...
    view full answer...
  • Can the Optronics Sealed, Miro-Flex Trailer Clearance Trailer Light Be Used as a Brake Light
    The 3 diodes in the Miro-flex light, # MCL51RB, would not make a very good brake light. They would not be as bright as the regular brake lights already on the trailer. You would need a light designed to function in whole or in part as a brake light such as # STL23R24B. With this light you would also need a wiring harness, # A47PB. To mount it you could use mounting bracket, # BK45BB and grommet # A45GB. You could also flush mount it using the mounting flange # A45BB.
    view full answer...
  • Will Optronics Submersible Trailer Light ST6RB Work on Malone Kayak Trailer
    The Submersible Trailer Stop, Turn, and Tail Light # ST6RB that you referenced is a great choice to replace the existing lights on your Malone Kayak Trailer. The light housing is designed to allow water to flow in and back out of the housing while being submerged. This light has 6 functions: stop, turn, tail, rear reflex, side marker, and side reflex, and will mount on studs with 2 inch centers. For the left-hand version of this light you will want # ST7RB. For a similarly sized light...
    view full answer...

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