If your bike is a little older, it may have narrow handlebars. These shims allow riders to use their current handlebars when up-grading to the new Kinekt Suspension Stem. Our Stem is designed to use 31.8mm diameter handlebars and these shims allow anything from 25.4mm or 26.0mm and up. Works with most older bars. Please contact us if you are unsure of size.Diameter handlebars to diameter needed:25.4 to 31.826.0 to 31.8