Description: Made of 6061 aluminum alloy, strong and durable. Length: 530, 550, 350mm; Diameter:25.4mm 30.8mm 30.4mm 27.2mm 28.6mm 31.6mm 31.8mm 33.9mm; Thickness of the tube: about 3mm. There is a safe line mark on the seat post. Please insert at least above the minimum safety line. Generally applicable to folding bike, BMX, electric car, mountain bike, etc. Specification: Material: Aluminum Alloy Color: Black Size Chart: Size 1: Dia. x L: 31.8x530mm/1.25x20.86inch Size 2: Dia. x L: 33.9x550mm/1.33x21.65inch Size 3: Dia. x L: 31.6x350mm/1.24x13.77inch Size 4: Dia. x L: 27.2x350mm/1.07x13.77inch Size 5: Dia. x L: 28.6x350mm/1.12x13.77inch Size 6: Dia. x L: 30.4x350mm/1.19x13.77inch Size 7: Dia. x L: 30.8x350mm/1.21x13.77inch Size 8: Dia. x L: 25.4x350mm/1x13.77inch Package Includes: 1 Piece Bicycle Seatpost Note: Color might be slightly different due to the color calibration of each individual monitor. Please allow slightly measuring deviation due to manual measurement.