What trailer coupler do I need for my ball size and tongue?

Answered by RV Parts Giant · Upland, CA · November 9, 2026

Short answer: Match three things: the ball size (1-7/8, 2 or 2-5/16 in, stamped on the old coupler or the ball), the tongue shape (a straight tongue of a given width, an A-frame, or a flat-mount plate), and a rating that covers the trailer's loaded weight. Our couplers run from a 1-7/8 in on a 2 in tongue to a 14,000 lb flat mount.

A replacement coupler has to match the trailer, not the truck. Three measurements decide it, and you can take all three off the old coupler and the tongue before you order.

1. Ball size

The coupler is made for one ball diameter. The common sizes are 1-7/8 in, 2 in and 2-5/16 in, and the size is usually stamped on the top of the old coupler. If it has worn off, read the size stamped on the ball the trailer has been towing on. Coupler and ball must be the same size; never mix them.

2. Tongue shape and width

This decides how the coupler bolts or welds on:

Tongue	What it looks like	Coupler we stock
Straight tongue, 2 in wide	a single tube running forward	Straight coupler for 1-7/8 in ball, 2 in tongue
Straight tongue, 3 in wide	a wider single tube	Dacromet bolt-on coupler for 2-5/16 in ball, 3 in tongue, 8,500 lb
A-frame	two rails meeting in a V at the front	Southwest Wheel 50 degree A-frame coupler for 2 in ball, 8,000 lb
Flat plate on top of the tongue	a flat mounting surface, common on heavier trailers	Flat mount coupler for 2-5/16 in ball, 14,000 lb, hardware included

Measure the tongue's outside width with a tape. For an A-frame, check the angle where the rails meet. The Southwest Wheel coupler is a stamped 50 degree helmet style, so it suits a 50 degree V.

3. The rating

The coupler's rating has to cover the trailer's loaded weight, which is on the trailer's VIN sticker as its GVWR. Then check that the ball and the ball mount on the truck are rated at least as high as the trailer too.

Two things people miss

A new coupler may need a new lock. Locks fit by ball size and coupler style. See which coupler lock fits a 2-5/16 inch or rolled-lip coupler.
Off-road trailers are a different part. If the trailer uses a Cruisemaster or ARK articulating coupler instead of a ball, see the off-road trailer coupler guide.

Not sure what you have? Send us a photo of the tongue and the stamp on the old coupler, and we will match it.