The tripod mount ring mount on the tripod， it helps you fix and balance your tele lens which is heavy or long lens hanging off the front of camera.

right weight and strong building by third party. 100% fits Canon and does have same construction.

Ring diameter: 66mm
Ring thickness: 3mm
Made by metal with very high quality
The UNC (Unified National Coarse Thread) is 1/4"

Suitable for:

Canon Lens

Canon EF 70-200mm f/4L USM
Canon EF 70-200mm f/4L IS USM
Canon EF 300mm f/4L USM
Canon EF 400mm f/5.6L USM

Contains:

tripod mounting ring x1