CLASS 1 - For trailers with a gross weight not to exceed 2,000 lbs. These couplers use 1-7/8" hitch balls. Couplers are labeled for over the counter sales. CLASS II - For trailers with a gross weight not to exceed 3.500 lbs. This coupler uses a 2" hitch ball. Coupler is labeled for over the counter sales. CLASS III - For trailers with a gross weight not to exceed 5,000 lbs. This coupler uses a 2" hitch ball. Coupler is labeled for over the counter sales.