USE's shims are made to 100mm length and are longer than other shims on the market. 25.4mm shims need to be so thin as they are etched down in acid to the correct tolerance and are too thin to anodise (show as silver).
USE Seatpost Shim
Seatpost Shim 25.4mm Seatpost To 27.2mm, Bike Seat Tube Sleeve Shim Adapter Tube Accessories Creative and Popular
Azarxis Bike Seatpost Shim Bicycle Seat Post Tube Adapter Shim Sleeve 100mm Aluminum MTB Bicycle Reducing Sleeve 25.4 27.2 28.6 31.8 to 27.2 28.6 30.4 30.9 31.6 31.8 33.9 34.9 (I.D.φ27.2/O.D.φ30.9)
Azarxis Bike Seatpost Shim Bicycle Seat Post Tube Adapter Shim Sleeve 100mm Aluminum MTB Bicycle Reducing Sleeve 25.4 27.2 28.6 31.8 to 27.2 28.6 30.4 30.9 31.6 31.8 33.9 34.9 (I.D.φ25.4/O.D.φ27.2)
Azarxis Bike Seatpost Shim Bicycle Seat Post Tube Adapter Shim Sleeve 100mm Aluminum MTB Bicycle Reducing Sleeve 25.4 27.2 28.6 31.8 to 27.2 28.6 30.4 30.9 31.6 31.8 33.9 34.9 (I.D.φ31.8/O.D.φ34.9)
CYSKY Bike Suspension Seatpost 27.2 x 350mm with Bike Seatpost Shim 28.6mm 30.9mm 31.6mm, Shock Absorber Bicycle Seat Post for Mountain Bike Road Bike MTB BMX