Nashbar Reduced Radius Rollers CNC machined aluminum drums, 85mm in diameter, feature sealed cartridge bearings for quiet, smooth operation 50" x 18" aluminum frame 9 length settings to fit most bicycles (compatible wheelbase range of 35.5" - 42") Frame has 3 sets of feet equipped with non-marring plastic fittings to protect floor finishes Connecting belt is constructed of polyurethane for long life