Apply to: If your handlebar diameter is 25.4mm and the stem diameter is 31.8mm, then you can use "25.4 to 31.8MM" handlebar shim as a conversion. Description: 1. Forged From High-Strength Aluminum Alloy, High Strength And Corrosion Resistance 2. The product adopts corrugated design for better anti-skid 3. This reducer allows you to use standard size handlebars of smaller diameter on a large shank. 4. Great replacement gear accessories for bike cycling enthusiasts. Specification: Material: Aluminum alloy Specifications: 25.4 to 31.8mm Color: Red Quantity: 1pair Package includes: 1pair x Bike Handlebar Conversion Shim