The Specialized 34.9 OD to 30.9 ID seatpost shim allows a 30.9 mm diameter seatpost to be used in a bicycle frame with a 34.9 mm seat tube. Made from lightweight aluminum, the shim provides a secure and precise fit without the need for adhesives or permanent modifications. It's commonly used to increase seatpost compatibility across different frame standards.

• Outer diameter: 34.9 mm

• Inner diameter: 30.9 mm

• Material: aluminum

• Installation: slip-fit, no tools required

• Purpose: adapts 30.9 mm seatposts to 34.9 mm frames

• Weight: approximately 10 g

• Compatibility: works with most round seat tubes and dropper posts