The CatEye Spacer X Rapid X/Rapid X2 Tail Light Mounting Bracket fits mounting areas between 21.5 and 32mm. Spare brackets are good things because they make it easy to switch your lights between bikes in your household. The rubber band is the same as the one CatEye supply to fit a Rapid X or Rapid X2 light. This is a rubber band that can be used again and again. The spacer makes it easier to fit a CatEye Rapid X or Rapid X2 light. Easy mounting instructions included on packaging. Fits mounting areas between 21.5 and 32mm. Applicable Models: Rapid X (TL-LD700-F/ -R). Rapid X2 (TL-LD710-F/ -R).