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Optronics Trailer Light w/ Flange, Weathertight Plug - Brake, Tail, Turn - Submersible - Round - Red
Optronics

Optronics Trailer Light w/ Flange, Weathertight Plug - Brake, Tail, Turn - Submersible - Round - Red

Part Number: STL42RMB
In Stock
$27.84
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4" Waterproof light displays brake, tail, and turn signals on your trailer. It mounts with the built-in flange and has a weathertight connector. Great Prices for the best trailer lights from Optronics. Optronics Trailer Light w/ Flange, Weathertight Plug - Brake, Tail, Turn - Submersible - Round - Red part number STL42RMB can be ordered online at etrailer.com or call 1-800-940-8924 for expert service.
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Optronics Trailer Lights - STL42RMB

Highlights

  • One Light, 3 Functions: Provides brake, tail, and turn signals so you stay visible and safe.
  • Reliable In Any Weather: Waterproof design keeps moisture out for dependable use on boat trailers.
  • Durable Build: Polycarbonate lens and housing resist impact and wear over time.
  • Tight, Clean Wiring: Weathertight plug blocks moisture for a secure electrical connection.
  • Bright, Efficient LEDs: 10 diodes use just 0.413A (stop/turn) and 0.026A (tail) at 12.8V.
  • Easy Replacement Fit: Built-in flange mounts in a 5-1/2" space with 4-1/4" hole spacing.

Features to know about

Brighter and More Efficient Lighting: 10-Diode LED Power

Upgrading to LED makes a noticeable difference in brightness and reliability. This 4" round Optronics light uses 10 LEDs behind a red lens to clearly display brake, tail, and turn signals. It glows for tail lights, brightens for brakes, and flashes for turns—all while drawing very little power. At 12.8V, it uses just 0.413 amps for stop/turn and 0.026 amps for tail light functions. That’s plenty of visibility with almost no strain on your wiring or power system.

Built for Wet Conditions: Fully Waterproof and Submersible Design

If your trailer ever sees rain or the boat ramp, this light is ready for it. The polycarbonate housing and lens are sealed together to make it completely waterproof and submersible. You don’t have to worry about water getting inside and ruining the LEDs or corroding the connections. It’s built to handle the same conditions that cause traditional bulbs to fail, keeping your lighting dependable even after repeated dunking.

Clean Fit Installation: Recessed Mount with Built-In Flange

Installing this light is straightforward thanks to its recessed mount design and built-in black flange. The overall diameter with flange is 5-1/2", and the mounting holes are spaced 4-1/4" apart center-to-center. It fits openings about 4-1/4" to 4-1/2" in diameter, giving you a snug, professional look without extra hardware showing. Hardware isn’t included, so you can choose fasteners that best suit your setup.

Reliable Power Connection: Weathertight Plug System

Poor electrical connections can ruin even the best lights, so this one comes prepared with a weathertight connector designed to block out moisture where it matters most. To complete the wiring, you’ll need adapter AL45PWTB (sold separately) to connect it to standard 3-prong plugs. For layout flexibility, pick up either a right-angle pigtail (A47PB) or straight pigtail (A45PB), both sold separately. Once connected, you’ll have a solid, sealed link that keeps your light working reliably through any weather.

Close-up of Optronics trailer light weathertight plug connector showing moisture-sealing design for secure trailer wiring connection

Road-Ready Compliance: DOT, FMVSS 108, and CMVSS 108 Approved

You can count on this light meeting all federal and Canadian lighting requirements right out of the box. It’s DOT compliant and built to the standards of FMVSS 108 and CMVSS 108, so you know your trailer lighting will stay safe and legal wherever you go.

Specs

Dimensions

  • Dimensions with flange: 5-1/2" diameter x 1-15/16" thick
  • Light face: 4" diameter
  • Distance between mounting holes (center on center): 4-1/4"

Optronics 4-inch round red LED trailer tail light with built-in black flange showing product dimensions and mounting hole spacing for brake, tail, and turn functions

Electrical

  • Compatible with: 12V DC systems
  • Power draw at 12.8V (Stop/turn): 0.413 amps
  • Power draw at 12.8V (Tail): 0.026 amps

Lighting

  • Diodes: 10

Warranty

  • Lifetime warranty on LEDs

STL42RMB Optronics LED Trailer Tail Light - Stop, Tail, Turn - Submersible - 10 Diodes - Weathertight Connection - Red Lens





Customer Satisfaction Score:

Ratings & Reviews

4.4

40 reviews
Review sort icon
4" Waterproof light displays brake, tail, and turn signals on your trailer. It mounts with the built-in flange and has a weathertight connector.

by:

Great service. easy process.



by:

A+++



by:

Excellent product and price.



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Service was great. Thanks.



by:

Fits the rebuilt of antique truck. Just what was needed. POSITIVE!



by:

work fine. thanks.



by:

Good service and good product



by:

Exelant quality and good price



by:

No gasket with light. The white lights I ordered had new gaskets. Had to use old gasket

Brooke M. profile picture
Etrailer Expert

Brooke M.

10/13/2021

Thank you for the review! Our customer service team should be reaching out to you in the near future.



by:

Good customer service



by:

Great addition



by:

Order was processed and delivered quickly. Exceeding my delivery expectations for ground. Continuous follow up on the order. Savings was great. Definitely will be back.



by:

I can't believe how thin and cheap this plastic junk is, for the price I thought they would be professional grade. They don't even include the plug that is required to install them.



by:

Thanks I received everything and it was what I expected. As I do more work on trailers I will be a returning customer.



by:

Was a perfect replacement for the old burned out lights on my Featherlite stock trailer!!!



by:

Light has worked great as expected! No issues and was direct replacement for original light.



by:

Worked great. Improvement to old style bulb lights!



by:

Perfect fit but connector has changed and you need to purchase Item # AL45PWTB to eliminate need to cut and splice factory wiring.



by:

Very bright, really like the weather tight connectors.



by:

Just what I needed to replace the old lights on my tow dolly. I had to make the holes slightly bigger to fit the unit in, but I’m hoping I won’t have to replace them again for a long time.



by:

Easy ordering and fast delivery. Only thing I will add is that the wiring connection on the back was different than mine and I had to order the connector harness that plugs into this new light and the old connection on my trailer. I don’t think this was mentioned in the product info. All is good! Thanks



by:

Perfect replacement fitment and excellent price.



by:

Nothing like ordering a product, waiting for it to arrive, only to discover it's useless without another part that's sold separately. You cannot wire this without an additional pigtail. This is the second time I've received a product from etrailer that required something else to be bought separately....

Heather A. profile picture
Etrailer Expert

Heather A.

9/12/2017

You are correct, this LED Trailer Tail Light requires a pigtail to wire it in. Part # AL45PWTB to fit industry standard 3 prong plugs or part # A45PMB for the hardwire version.


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See what our Experts say about this Optronics Trailer Lights

  • Replacement Trailer Taillight for ST-40 RS
    Hey Richard, I did some digging and that part number looks to cross reference with the part # STL42RMB for an LED replacement. This is a recessed mount 4 inch diameter trailer taillight.
    view full answer...
  • Looking For Replacement Round Tail Light Kaper II L15 0072 On 2019 Fleetwood Bounder 33C
    Hello Linda. We do offer several round tail lights which very well may work on your 2019 Fleetwood Bounder 33C, although we do not have a direct replacement for the Kaper ii L15 0072 LED since we do not carry this brand. I was not able to find any specs online for this Kaper ii L15 0072 LED that would tell me the exact size though. In the pictures I found, it looks very similar to the Optronics LED # STL42RMB. This light is 4" in diameter with the flange being 5-1/2" in diameter. Please...
    view full answer...
  • Recommended Trailer Tail Lights for 4.25 Inch Opening
    The LED Trailer Tail Light # STL42RMB has screw mounting holes that are 4-1/4 inches on center. The smallest hole this light will fit is 4 inches. You will have difficulty mounting this light as your opening matches the mounting hole locations so you won't get proper hold. You may want to use the Rubber Grommet for 4" Round Trailer Tail Lights # A45GB along with the # STL55RB which won't use any screws to mount. You will also want the 3 wire pigtail # A45PB.
    view full answer...
    Image 1 for
  • Replacement Taillights for 2022 GMC Baybridge Cutaway Box Van Th
    A lot of box van and service body lights are trailer taillights like the # STL42RMB that you referenced so it would not surprise me if this is what you have/need. If yours measures 5-1/2 inches in diameter overall then this would work great as an easy replacement and would wire in pretty easy as well.
    view full answer...
  • How to Determine Correct Replacement Round Tail Light For Trailer
    Thank you for the photo; and while we can tell you how to determine the correct replacement round, red tail light for your trailer, we don't have any way of knowing the exact light because unfortunately there isn't any type of list of replacement parts for trailers (the SAE number on that is not a part number, SAE stands for Society of Automotive Engineers and means it passed its standards test). So in order to determine this, however, you will simply need to measure your tail light and...
    view full answer...
    Image 1 for
  • Will 4" Round LED Light Fit 4" Recessed Opening
    The LED Trailer Tail Light # STL42RMB you're looking at has a lens with a 4" diameter but the hole needed to install it needs to have about a 4-1/4" to 4-1/2" diameter. This is the case with all of the 4" diameter lights though so you might end up needing to make the hole a little larger so you can install a light. Please note that this has a plug at the back side of it so you'll need the 3-Wire Pigtail # A45PMB as well to connect this to your trailer wiring.
    view full answer...

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Info for this part was:

Employee Leah B
Edited by:
Leah B
Employee Lindsey S
Updated by:
Lindsey S
Employee Brian T
Updated by:
Brian T
Employee Amanda K
Updated by:
Amanda K
Employee Jameson C
Expert Research:
Jameson C
Employee Cole B
Installed by:
Cole B
Employee Amy B
Written by:
Amy B

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