The item description says it has an o-ring clamp for a variety of tube sizes, but the photo shows a fixed clamp and screw attachment. I received a bell with a clamp and screw that fits only 22.5 to 25.4 mm diameter tubes. I had to return it, and I'll look for something else that fits my 31.8 mm diameter handlebar. it's a nicely made product, but the web page description and specifications need to be updated.