Features: Premium aluminum bicycles seatpost shims converts 27.2mm seatposts to fit 28.6/30.4/30.8/31.6mm frames with light weight durability for secure cycling performances. Engineered at 59mm length, this seatpost adapter ensures vibrations simple installation while maintaining optimal saddle height and riding comfort. Ideal for mountain bike enthusiasts, road cyclists, and commuters needing reliability compatibility across multiple bike types including folding cycles. Effortlessly upgrade hybrids bikes or repair vintage frames during trail adventures, commutes, or bike customization projects. This universals bike seat tube converter requires tool for installation, enabling quick adjustments between varied terrain challenges. Specifications: Color:Four Choices Dimension:31.6×59mm/1.24×2.32in 28.6×59mm/1.12×1.07in 30.8×59mm/1.21×2.32in 30.4×59mm/1.19×2.32in Component:Aluminum alloys Package Includes: 1pc seat tube diameter change sleeve note: 1.Please allow 1-2cm errors due to manual measurement, making sure that you will not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual color.