This Tripod Mount Ring is designed for Canon RF100-400mm F5.6-8 IS USM lens, the lens did not design a tripod mount ring, with this ring, you can place the lens on the tripod to balance the weight and shoot Vertical or horizontal. It features Arca-compatible dovetail which allow you attach your lens to Ball Head, Clamp or Panorama Head of Arca-Swiss standard. The Anti-slide bottom can prevent your lens from accidentally slipping out of the quick release adapter, Security screws and hex wrench are included for free. Installation Guide: 1,Loosen the screw on the collar by turning counterclockwise. 2,Slightly expanded the gap with your fingers or tools. 3,Install the lens when the ring expanding (this action may flip the switch on the lens side) 4,Adjust position and tighten screws (Please confirm the switch position on the lens side before tightening,Do not tighten the screws too much as it may damage the lens.)