Product: MTB / Bicycle Seatpost Shim Tube Sleeve Reducer — Seatpost Converter Adapter What it does Converts mismatched seatpost and frame tube diameters so you can fit a smaller seatpost into a larger seat tube without modification. Acts as a simple, removable sleeve that restores a secure, centered fit and prevents creaking or movement. Key benefits Durable material: Made from aluminum alloy for longlasting performance, corrosion resistance, and low weight. Precision machining: Accurately manufactured to tight tolerances so the shim fits concentrically and solves common size mismatch problems. Wide compatibility: Available in multiple models to cover a broad range of seatpost sizes, providing versatile compatibility options for different seatpost/frame combinations (models ranging from 4 to 33 and 4.9). Easy to use: Simple to install and remove — no special tools or frame modification required. Protects components: Reduces wear on the seat tube and seatpost by providing a proper bearing surface and preventing direct metalonmetal contact. Specifications and function Product type: Seatpost shim / tube sleeve reducer / seatpost converter adapter for MTB and bicycles. Material: Aluminum alloy. Function: Sleeve adapter to match differing seatpost and seat tube diameters and ensure a secure fit. Practical use scenarios Upgrading or swapping bikes: Move a favorite seatpost from one bike to another when the seat tube diameters differ. Temporary or travel use: Carry a lightweight adapter to use when a replacement post isn't available while traveling or on a ride. Component compatibility during upgrades: Fit a newly purchased seatpost that is smaller than your frame's seat tube without reaming or expensive frame work. Why choose this adapter Reliable, machined aluminum construction for dependable performance. Solves a common compatibility issue quickly and cleanly without altering your frame or seatpost. Multiple model options let you match the adapter to your exact seatpost/frame combination. Note: Select the correct model size for your seatpost and seat tube to ensure a secure fit.