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. * This Tripod Mount Ring is made by third party but 100% fits Canon and does have the same construction., it replace CANON TRIPOD MOUNT RING AII (W) * For Canon EOS 70-200MM F4L, EF 70-200MM F4L IS, EF 300mm f/4L USM. EF 400MM f/5.6L USM * The ring has a fabric interior so it will not damage your lens. * 100 % Brand new, original box packaging!