MOUNT BOX ONE CLAMP 31.8 BLACKThe Box One 31. 8 shifter clamp is an accessory that converts any Box shifter to be compatible with modern drop handlebars found on gravel, cyclocross, and commuter bikes Hinged clamp design is easy to install without having to remove grips or tape Compatible with all Box shifters as well as some other brands 31. 8mm clamp only, shifter or brake not included