EXMAX Tripod Mount Ring A(W) Lens Collar For Canon EF 100mm F/2.8 F2.8 USM Macro Lens Designed for Canon EF 100mm f/2.8L IS USM Lens. Tripod mount ring, helps you fix and balance your tele lens which is heavy or long lens hanging off the front of camera. With 1/4 screw hole, convenient to be mounted on the tripod. Surface hardening treatment, fine and smooth, wear-resistant Made by metal with very high quality