How to Determine Correct Replacement Tail Light Lens for Trailer

Updated 09/02/2025 | Published 09/29/2019

Question:

do you have a replacement red lens cover for keystone springdale rv sae ap2 dot 14

asked by: Jean

Expert Reply:

While I can help you determine exactly how to figure out what replacement lens you need, trailer manufacturers don't manufacture a list of replacement parts for models of trailers, and SAE actually stands for "Society of Engineers" and isn't a part number for the light, it just means it has passed certain standards.

Having said all that, in order to determine the correct replacement lens, a part number (which may be on the light itself) is needed, or you may be able measure to determine what light you have and get the lens from that. Otherwise, you'll need to replace the entire light assembly; you will simply need to measure your current tail lights and find the one that most closely matches your measurement, and also know if your lights are surface mounted or recessed mounted.

For example, the Optronics Fleet LED Trailer Tail Lights # TLL12RK have a light face which is 6-1/2" long x 2-5/16" tall and are recessed mounted.

If you let me know what your light measures and how they mount I would be happy to try and find the best replacement for you. I have also added a link to our entire selection of tail lights for you to check out, which you can filter by size once you measure your lights.

expert reply by: Kyle S

Kyle

8/30/2025

I have a custom made tear drop trailer, My back right Turn,brake, tail light, the brake light quit working. Its LED light. How do you determine the the lens replacement size? is it measured from the light itself or do you measure the outside diameter of the lens cover? Its a 3 wire lens as well. If I measure the outside diameter of the lens cover its 41/4 "and the inside is 31/4". Kyle

Gwendolyn Y.

9/2/2025

@Kyle That's a good question. Our measurements would be for the outside of the lens. Is your light an oval shape or more circular? I looked at what lenses we had that were 4-1/4" diameter and we have part numbers # 338-15R, # 415-15R, and # 410-15R. Depending on the brand, there may be a part number on the back of the light housing. All Optronic lights will have a part number on the back. If you see an SAE number, that is just a code used to indicate that the night has passed the Society of Automotive Engineers (SAE) guidelines. Let me know what you find out and I'd be happy to do some more searching for ya!