This is a professional bicycle accessory. After installation, the height of the bicycle seattube can be adjusted through the handle, making the operation simple and making your cycling more comfortable. Features: The seattube is made of aluminum alloy material, with high strength, fine corrosion resistance and wear-resistant for long lifespan. The seatcushion angle can be adjusted through the clamping plates. The hydraulic structure can be locked at any position, frameless, and more comfortable to ride. The sealring design is waterproof and dustproof, which effectively protects the inside cleaning of the seattube. The surface of the seattube adopts anodic oxidation process, which is corrosion-resistant, high-temperature resistant, wear-resistant, and scratch resistant, protecting the metal surface. Clear scale for more convenient adjustment. Specifications: Type (seatpost diameter*seatpost length): 31.6*380mm, 30.9*380mm, 31.6*445mm, 30.9*445mm (optional) Main color: black Material: aluminum alloy Stroke: 31.6*380mm, 30.9*380mm: 100mm 31.6*445mm, 30.9*445mm: 125mm Package size: 480 * 120 * 60mm / 18.9 * 4.7 * 2.4in Package weight: 740g / 1.6lb Packing List: 1 * Bicycle Seatpost