What hitch ball shank size do I need for my ball mount hole?

Answered by RV Parts Giant · Upland, CA · October 31, 2026

Short answer: The shank diameter must match the hole in your ball mount. TowSmart's Class 2 mount has a 3/4" hole, its Class 3 X-mounts have 1" holes and its Class 4 forged mounts have 1-1/4" holes. The ball size is a separate choice set by your coupler, and the lowest-rated part sets your towing limit.

A hitch ball has three numbers: ball size, shank diameter and shank length. Each one answers a different question, and mixing them up is the usual reason a ball arrives that will not fit.

Number	Set by	Options we stock
Ball size	Your trailer coupler	1-7/8", 2", 2-5/16"
Shank diameter	The hole in your ball mount	5/8", 3/4", 1", 1-1/4"
Shank length	The thickness of your mount at the hole	Varies by ball variant

Hole size by TowSmart mount

Model	Class and rating	Hole
700	Class 2, 3,500 lb	3/4"
702 and 704	Class 3, 5,000 lb	1"
737 and 738	Forged, up to 17,000 lb	1-1/4"

If you have another mount, measure the hole itself with a caliper or a drill bit shank. Do not go by the class alone.

Checking shank length

The threads must pass through the mount with room for the included lock washer and the full nut. Measure the mount's thickness at the hole, then compare that to the shank length on the ball variant you are choosing. If the nut cannot fully engage, choose a longer shank.

The rating trap

Our chrome hitch balls are rated from 2,000 lb to 12,000 lb, depending on the variant. The 737 and 738 mounts are rated up to 17,000 lb. Put a 12,000 lb ball on a 17,000 lb mount and you have a 12,000 lb setup at best, because the listing's rule is to match the ball rating to the lowest-rated part of your towing setup.

That list includes your receiver and your tow vehicle's tow rating as well. A strong mount does not raise either of them.

The same rule applies to adjustable mounts with a combo ball. On Andersen's Rapid Hitch, for example, the hitch's rating for your shank size can be lower than the ball's own rating; our Andersen Rapid Hitch and EZ Hitch guide lists both.

Want to skip the ball entirely?

The Class 3 starter and security kits come with a 2" ball already included, along with a 5/8" pin. Those are a simple way to avoid the shank question on a 5,000 lb setup.