DJC Bike Suspension Seatpost Shock Absorber Damper Post 27.2 28.6 30.0 30.4 30.9 31.6 33.9 mm, Lightweight Aluminum Body   Features Spring Coil Suspension: Build-in spring coil and damper rubber absorb the vibration while riding, the seat post comfort your riding experience, improve the shocks. Rebound force adjustable by tighten or loose the bott..