CURT Class 4 Trailer Hitch Ball Mount, Fits 2-Inch Receiver, 12,000 lbs, 1-1/4-Inch Hole, 2-In Drop, 1-Inch Rise Model 45312CURT Class 4 Trailer Hitch Ball Mount, Fits 2 Inch Receiver, 12,000 lbs, 1 1 4 Inch Hole, 2 In Drop, 1 Inch Rise Model 45312 When you demand more from your towing equipment, CURT class 4 ball mounts answer the call. Our heavy duty ball mounts are constructed from quality steel and feature a 2" x 2" shank. They are built to complement CURT class 4 trailer hitches and are perfect for towing large boat trailers, RVs, livestock a nd horse trailers as well