Coupler allows height of trailer tongue to be adjusted to height of towing vehicle for level towing. Fits inside #12874 and #12875. Max. Gross Trailer Weight lbs. 12,500, Length in. 10, Fits Ball Size in. 2 5/16. 10 in. overall length Fits inside 2 7/8 in. wide channel Fits 2 5/16in. Ball Trailer Weight of 12,500 lbs.