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When you’re on the road, you need a light that clearly signals every move. This round Optronics tail light handles stop, turn, tail, and license plate illumination all in one 3-7/8" package. The built-in license plate light shines down on your tag so it stays visible and compliant, while the red lens over the incandescent 1157 bulb gives bright, even output. Designed for 12V DC systems, it draws 2.3 amps on stop/turn and 0.9 amps on tail, keeping your signals strong and consistent.
Road vibration and bumps can take a toll on trailer lights, but this one’s ready for it. The shock-proof socket keeps the bulb seated securely and guards against damage from impact. Around it, a tough steel housing with a screw-on lens protects the internal parts from debris and moisture on dry roads. It’s DOT compliant too, so you can count on it for dependable performance mile after mile.
Setting it up is straightforward—just use the included studs to surface mount it with 2" center-to-center spacing. The 2-wire setup includes a power lead and ground wire, so there’s no guesswork when connecting to your trailer wiring. Once mounted, the round shape sits neatly against the surface for a clean look that blends in well with most trailer setups.
No need to replace the whole light if a bulb ever goes out. The screw-on lens removes easily so you can swap in a standard 1157 double-contact bulb in minutes. That keeps upkeep simple and affordable without tools or complicated disassembly—just replace the bulb and you’re ready to get back on the road.
Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.
Today, we're going to be reviewing Part Number ST21RS. This is the Optronics Trailer Light for the driver side. The round trailer light is going to serve as your brake light, turn signal, and tail light. It's got the built-in license plate light as well. It's got the red, acrylic lens. It's very simple to replace.
It attaches with the two included screws. It's going to feature the easy-to-change incandescent bulb that's going to sit in a shockproof socket for a long bulb life. It's got the black, enamel-coated steel housing. It's very durable and strong, as well as corrosion resistant. Here on the back, it's going to expose the two lead wires to connect your light, and it's going to ground through the mounting hardware. The mounting hardware is included.
It's going to surface mount using those two studs on the back of the housing. They just slide into the channels here, and then you can adjust them as needed to fit your application. This light is designed to extend out from the trailer. It is Department of Transportation compliant. Again, it's for the driver side. If you need a light for the passenger side, you can use Part Number ST20RS, and you can find that right here at etrailer.com.
This light is going to give us an overall diameter of 3-7/8", with an overall depth of 3-1/16". The bulb type is 1157 double filament. The power draw is at 12.8 volts, so for the brake light, it's going to use 2.3 amps, for the turn signal, it's going to use 2.3 amps, and for the tail light function, it's going to use 0.9 amps. When installed, those two studs here on the back are going to give us a measurement, center on center, 2" apart from one another. We're going to go and hook this up to our external power source, that way, you can see what it looks like with power running to it, and with our overhead lights turned off. The red wire is going to be for the tail function, so we'll go ahead and connect that.
Then the black wire is going to be for our stop and turn signal. You can see here that it's going to send out a nice, consistent signal. You got the license plate illuminator here at the base, and then when we apply there brakes, it's going to illuminate for a more consistent, even brighter signal. It's going to have that same function for the turn signal as well. That's going to do it for our review of Part Number ST21RS. This is the Optronics Trailer Light for the driver side. .
Ratings & Reviews
Gary W.
3/12/2017
No problems-working well. Thanks for checking.
Brooke M.
11/27/2024
gosh, I am so sorry to hear that, Kenneth. Let me look into this and get you the correct parts in the mail!
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Steven
9/14/2021
Excellent product ..rat rod is certainly enhanced with these lights. I am very pleased .