Seat post shim tube converter for MTB and road bikes — a precision aluminum sleeve that lets you fit a seatpost to a frame with a different seat tube diameter. Key benefits Fixes mismatched sizes: precisionmachined shim fills the gap between seatpost and frame, eliminating wobble and making an incompatible seatpost usable. Durable, lightweight solution: made from quality aluminum alloy for long service life without adding significant weight. Simple and fast installation: insert the sleeve, set the seatpost height, and clamp — no special tools or frame modification required. What it does Allows a smaller seatpost to be used in a larger seat tube or vice versa by reducing the internal diameter to the correct size. Improves seatpost stability and prevents sidetoside movement when sizes don't match. Compatibility and models Designed to fit seat tubes with an internal diameter range from 2mm to 34.9mm. Multiple size options available to suit common combinations (examples): 2mm to 25.4mm, 25.4mm to 27.2mm, and additional sizes to match your seatpost and frame pairing. Choose the model that matches your frame's inside diameter and the outside diameter of your seatpost. Material and performance quality aluminum alloy construction: balances strength and low weight. Precision machining ensures a snug fit and consistent clamping force to protect the frame and seatpost. Sleek finish enhances bike appearance while remaining functional and unobtrusive. Easy installation (quick steps) 1. Open the tube clamp on your frame. 2. Insert the converter sleeve into the frame seat tube. 3. Insert and set the seatpost to the desired height. 4. Tighten the tube clamp securely. Practical use scenarios Upgrading to a aftermarket seatpost that has a different diameter than your frame. Swapping seats between bikes with different seat tube sizes during group rides or races. Installing a dropper post or specialty post that requires a different diameter than your current frame. Notes Verify both your frame's internal seat tube diameter and your seatpost's external diameter before selecting a model. Handles common mismatches without permanent frame changes. Materials: quality aluminum alloy Fit range: seat tube diameters from 2mm to 34.9mm Available models: includes 2mm to 25.4mm, 25.4mm to 27.2mm, and other size options to match your needs