Material: Aluminum Alloy. You can know the specifications of the reducer sleeve.
Sawhamale Aluminum Alloy Bicycle Seatpost Clamp with Rear Rack Mount, 33.5-34.9mm Diameter Adapter for Bikes Without Eyelets, Black Cycling Cargo Carrier Bracket
DJC Bike seatpost Shim Adapter 60mm 22.2 25.4 27.2 28.6 30 30.4 30.9 31.6 33.9 34.9 mm Aluminum MTB seat Post Tube Adapter
DJC Bike seatpost Shim Adapter 100mm 60mm 22.2 25.4 27.2 28.6 30 30.4 30.9 31.6 33.9 34.9 mm Aluminum MTB seat Post Tube Adapter
SL7 Handlebar Fork Internal Cable Compression, Road Bike Headset Expander Adapter, Aluminum Alloy Steerer Tube Fitter, Adjustable Diameter 22.9-25.4mm
Tapered Fork Headset Adapter Aluminum Ring for Converting Frame Headtube to Accept Larger Diameter Fork Steerer Tubes (A)
KREMORV Bike Seat Post Shim Bicycle Seat Post Tube Adapter Aluminum Alloy Seatpost Reducing Sleeve for Mountain Bike Road Bike MTB BMX
