4Pcs/Box MTB Bike Hydraulic Disc Brake Caliper Concave and Convex Washer Spacer Bicycle M6 O Ring Gasket Screw Fastener. -Professional Design: These concave-convex washers are CNC machined and chamfered for burrfree finish and perfect fit, will not wobble or dislocate like those washers with sphere surface do.
