Made of aluminium alloy material,lightweight and durable. Full CNC precision machining,anti-slip. Use this seatpost sleeve adapter ring, you can change the bicycle seat tube to the size you want. Suitable for MTB bike, mountain bike, road bike etc. Please check your bike frame seat tube outside diameter. Measure the inside diameter of your old clamp. Or measure the outside diameter of your seat tube (on your bike frame). Then make a right choice. Specification: Material: aluminium alloy Color: Black Size: 25.4mm to 28.6mm: Length: 60mm/2.36inch; Weight:21g Size: 27.2mm to 28.6mm: Length: 60mm/2.36inch; Weight:10.7g Size: 27.2mm to 30.4mm: Length: 60mm/2.36inch; Weight:22.3g Size: 27.2mm to 30.8mm: Length: 60mm/2.36inch; Weight:25.7g Size: 33.9mm to 34.9mm: Length: 40mm/1.57inch; Weight:5.6g Size: 27.2mm to 31.6mm: Length: 60mm/2.36inch; Weight:32.2g Size: 27.2mm to 33.9mm: Length: 60mm/2.36inch; Weight:50.2g Size: 27.2mm to 25.4mm: Length: 60mm/2.36inch; Weight:18.4g Package Includes: 1 Piece Seat Post Tube(2 Pack) Note: Please allow slightly difference due to manual measurement. Color may be slightly different since different monitor. Thanks