Standard metal saddle rails are 7 mm in diameter and most carbon rails are 9 – 9.25 mm diameter. In order to allow for this larger size, it is necessary to add two M5 washers to each screw during the installation process.
 
This kit includes the hardware required to install certain XLAB systems onto these enlarged 7 x 9 mm carbon rails.
 
Note: Not designed to work for uniquely-shaped rails beyond circular, oval-shaped rails.
  
Systems that might require this kit, if you have oversized carbon rails:

Wing Series: Turbo Wing, Super Wing.
Delta Series: Delta 400, 425, 430.