These outboard PF30 cups are machined out of 6061-T6 aluminum, and specifically designed to house 9mm thick "Spanish" style BMX bearings. The set comes standard with 22mm bore bearings, one 6mm bearing cover/cone for the non-drive side, one 2mm washer, two 1mm washers, and a 77mm internal spacer designed for 73mm wide bottom brackets. Enduro bearings are available as an upgrade.