DSLRKIT Full Metal Tripod Mount Ring for Nikon AF-S NIKKOR 70-200mm f/4G ED VR lens Replacement for Nikon RT-1 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. Made by metal with very high quality Suitable for Nikon AF-S NIKKOR 70-200mm f/4G ED VR lens Suitable for Nikon AF-S NIKKOR 300mm f/4E PF ED VR lens