What You're Actually Buying
This is a light kit, not just a lens — you get the oval-shaped stop/turn/tail unit plus the grommet and pigtail setup needed to mount it. Oval lights like this run the perimeter of trailers for tail, stop, and turn function all in one housing, which is why they're everywhere on Utility, Wabash, Great Dane, and similar trailer builds.
F01819S125 is the number stamped on the kit itself or on the box if you bought it as an OE-style trailer part. It's a sealed unit in most cases, meaning if the light's dead, you're replacing the whole thing rather than fishing for a bulb.
Fits wherever the trailer manufacturer speced this exact oval kit — check your trailer's build sheet or the number on the light you're pulling off before you order.
Why These Cross-Reference Numbers Match Up
Optronics, Peterson, and Grote all build ovals to the same mounting pattern and wire-out configuration as this kit, which is how STL78AB, TLL9RK, M423A-4, and the 47122-3 end up crossing to F01819S125. Same shape, same grommet size, same three-wire (or two-wire depending on application) hookup.
Where you need to slow down: not every oval light is wired the same. Some are 2-wire (combined stop/tail) and some are 3-wire (separate stop and turn). Check the pigtail on your old light — if it's got 3 wires coming out, you need a 3-wire replacement, not a 2-wire one, even if the housing looks identical.
Also watch grommet diameter — most of these are a 2-inch or so oval grommet, but not universal across every trailer brand. Pull the old light, measure the grommet hole, and match wire count before you order. If the numbers match what's stamped on your old part, you're in good shape.
Ordering From PartStop
We stock this in Tacoma and most orders that come in before early afternoon ship same day. If you're a local fleet needing lights in a hurry, call ahead and we'll have it at the counter.
Ship nationwide too, so if you're not near us, no issue — comes with a 6+ month warranty like the rest of our electrical stock.
Confirm by the number on your old light or your trailer's VIN/build sheet before ordering. Cheap part, annoying comeback if it's the wrong wire count or grommet size — five minutes checking saves a return.
F01819S125 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to F01819S125. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Optronics | STL78AB, STL78ABP, TLL9RK, TL38RB, STL39RB, STL101RFBP, STL101RCFBK |
| Peterson | M423A-4 |
| Cross-Reference | F01812-RS125, F01815S125, F01822S125, F00858S125 |
| Grote | 47122-3 |
Frequently asked questions
Does F01819S125 fit my utility trailer?
Likely, if your trailer uses a 3-wire oval stop/turn/tail light with a similar grommet setup — but confirm against the number stamped on your old light or your trailer's build sheet. Utility trailers built by different manufacturers over the years don't always use the same wire count.
Is this the same as the Optronics STL78AB?
They cross-reference and are built to the same mounting and wiring pattern, so functionally they do the same job. Aftermarket parts from different brands aren't identical down to every detail, so double check wire count and grommet size against your old part before ordering.
How do I know if I need the 2-wire or 3-wire version?
Pull the old light and count the wires coming out of the pigtail. Two wires means combined stop/tail function; three wires means stop and turn run separately. Don't guess — wrong wire count means it won't hook into your trailer harness right.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.