massmall Fixed Gear Mountain Bike MTB Road Cycling Track Bike Seatpost Clamp 31.8mm 1.Color:Black 2.Material: Aluminum Alloy 3.Fixed Bolt Seat Clamp for Better Seatpost Security 4.Theft Prevention For27.2mm Seatpost 31.8mm clamps fit 27.2 seatposts Road 5.Compatible with BMX, Mountain, Fixed Gears, Fixies, Track, Singlespeed Bikes