The Omnibell has an adjustable band clamp. Its ingeniously designed dinger can be rotated to any position. This gives you flexibility in mounting the bell anywhere on your handlebar, making it very convenient to use either your thumb or another finger to ring the bell. Dome Diameter: 34mm (1.34"). Fits handlebars with 22mm - 31.8mm (.87" to 1.25") outside diameters.