Profile Racing 19mm Spline Drive Sprocket Reach_53mm Uppers come as complete upper Frame Number:39 Uppers come as complete upper set including compression washer and topcap starnut based on the same proven rubber as the popular Donnasqueak but with an all over smoother tread for more grip and sidewalls which sits further round the side of the wall for better grind performance NOTE: Spline drive sprockets are not compatible with 2 piece cranks for Right Side Drive (not enough room for splines) • These can be used with all 19mm 48s spline cranks but Profile have some specific no boss Profile Cranks for a clean look and lighter set up