SRAM Centerline 2 Piece Mountain Bicycle Disc Brake Rotor, 180mm Material: [center] aluminum, [brake track] steel Attachment Type: 6-bolt Diameter: 140 mm, 160 mm, 180 mm Claimed Weight: [140mm] 86 g, [160mm] 102 g, [180mm] 125 g Recommended Use: mountain bike, cyclocross, road disc