Converts your diaphragm spring to six coil springs. Provides a more positive, controllable engagement. If you are building a performance bike or pulling heavy loads, two-up riding, etc., then your bike really needs this part. Fits: Yamaha 96-01 Royal Star XVZ1300RS; 05-08 Royal Star Tour Deluxe XVZ13CTV; 99-05 Road Star XV1600 / 1700RD; 02-05 Warrior XV1700WR; 99-08 Venture XVZ1300VN