Harrison Specialties Studded Motorcycle Drivers Backrest to fit Corbin Seats Studded Motorcycle Driver Backrest for Corbin seats Fits Corbin and other seats that accept a backrest with a 5/8" square stem that is 4.5" long. Pad angle is adjustable and has 2" of foam padding for comfortable back support. A smaller verison - 7" x 7" of this backrest is also available for sport bikes.