Features:_x000D_1.Shock Absorber: The Bike seatpost dapmens vibration effecitvely as it the bike seatpost can change the amount of force required to better abosorb the vibration according to your body shape._x000D_2. SizeMaterial: Attention In Advance: Please measure and check the diamater of your current bike seat post sizes before ordering.Made with Alluminum Alloy_x000D_3. Dustproof Ring: The dustproof ring on the shaft of the mtb seatpost can keep inner spring coil and damper rubber from gravel,dust or sand for longer use_x000D_4. Various Use: bicycle seatpost offers easy-to-set,secure,durable use which makes this bike seatpost shock absorber available for mountian bike, BMX bike, commuter bike._x000D_5. Height Adjustable, seat tube diamete: the original is 27.2mm, but some offers combo of seat tube and adjust-diameter Accessory via which can it be adjusted to 30.030.430.831.633.9mmPackage List:_x000D_Choice 1: 1 x seat tube_x000D_Choice 2: 1 x Seat tube with adjust-diameter Accessory