Use 25mm Seatpost Shim
The USE shim system allows you to fit a seat post into virtually any frame size. Our shims are made to 100mm length and are longer than other shims on the market giving your seat post much better support inside the frame. All shims are designed with a "top lip" to stop shim sliding into the frame.
Shims are available in Aluminum or Thermo Plastic, despite the latter being a lighter solution its material characteristics limit the thickness of the ID - OD measurements. Aluminium is used to achieve the thinnest shims as it is a more robust material.
Machined Aluminium shim - machined to very high tolerances from 6082 T6 Aluminum and then black anodised to protect from corrosion.
Machined Plastic shim - larger size shims are machined to very high tolerances from "filled" engineering thermoplastic UPVC. This keeps the weight down, as the shims get thicker.