Automotive Reference
Three ball diameters cover almost every trailer — and the ball must match the size stamped on the coupler exactly. Here's the sizing, the capacities, and the hitch classes.
Ball diameter must equal the coupler. Shank diameter and the ball's stamped rating set the capacity. Rise/drop lines the ball up with the trailer.
| Ball diameter | Typical trailer weight (GTW) | Common shank |
|---|---|---|
| 1-7/8" | Up to ~2,000–3,500 lb | 3/4" |
| 2" | ~3,500–12,000 lb (by shank & rating) | 3/4"–1" |
| 2-5/16" | ~6,000–30,000 lb | 1"–1-1/4" |
2" is by far the most common. Capacity depends on the ball's stamped rating and the shank — a 2" ball can be rated anywhere in that range, so read what's stamped on top.
| Class | Receiver opening | Max GTW | Typical use |
|---|---|---|---|
| I | 1-1/4" | 2,000 lb | Bike racks, tiny trailers |
| II | 1-1/4" | 3,500 lb | Small utility, small boats |
| III | 2" | 6,000–8,000 lb | Most trucks/SUVs, mid trailers |
| IV | 2" | 10,000 lb | Large trailers, campers |
| V | 2" / 2-1/2" | 12,000–20,000 lb | Heavy hauling |
Whatever size is stamped on your trailer's coupler — usually 2", sometimes 1-7/8" for small trailers or 2-5/16" for heavy ones. The coupler is marked; match it exactly, and check the ball's weight rating covers your loaded trailer.
No — never. It will seem to latch but the coupler can lift off the smaller ball under load. Ball and coupler diameters must be identical. This mismatch is a leading cause of trailer separations.
The shank is the threaded stud that bolts through the ball mount. A thicker shank (1" or 1-1/4" vs 3/4") carries more load, so heavy balls use bigger shanks — and the ball mount hole must match.
GTW (gross trailer weight) is the total loaded trailer weight the hitch can pull. Tongue weight is the downward force on the ball — usually about 10–15% of GTW. Both are stamped on the hitch and ball; stay under the lowest-rated part in the setup.