Description About this item 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. It features Arca-compatible dovetail plate which allow you attach your lens to Ball Head, Clamp or Panorama Head of Arca-Swiss standard. Reserved multiple 1/4″-20 & 3/8″-16 thread screw holes at the bottom for attach lens to tripod directly. Made of aviation aluminum alloy and CNC precision machining, anodizing surface treatment, right weight and strong building. Compatible with Sigma 105mm f/1.4 DG HSM Art (EF/FX/FE/L-mount) & For Sigma 100-400mm f/5-6.3 DG DN OS (E-mount, L-mount); Note: NOT compatible with Sigma 100-400mm f/5-6.3 DG OS HSM Contemporary ( EF Mount, Nikon F Mount ) lens and other lenses