Aluminum alloy + imported high temperature resistant material, a perfect replacement for the ceramic piston, to prevent side leakage, make the brake safer, full and longer braking force, good sealingStrip groove design, reduce heat transfer contact area, increase air flow shuttle, Conducive to heat dissipation.Colour: BlackMaterial: aluminum alloy + high temperature resistant materialSize: 21.9 x 9mmPackage Contents:4 x piston4 x piston seal ring4 x disc brake Sealing ring8 x five-line sealing ringOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.