Body aluminum 6061 alloy. Sand blast anodized surface treatment. A spring coil and damper rubber inside. Absorb the shocks and offer you comfortable experience. Shock absorb travel 40mm/1.73in, seatpost total length 350mm/13.7in. The seatpost fit for riders weight 50kg/ 110lbs to 100kg/ 220lbs. Bottom screw can adjust spring resilience. Clockwise the bottom screw if you are heavy, and anticlockwise it if you are lightweight. Good for city bike, lady bike, and daily leisure bikes. No clamp with the seatpost. Make sure you checked what diameter you need before buy. Specification: Size: Diameter: 25.4mm, weight: 429g Diameter: 27.2mm, weight: 478g Diameter: 28.6mm, weight: 515g Diameter: 30.9mm, weight: 516g Diameter: 31.6mm, weight: 538g Package Includes: 1 Piece Seatpost