Micnova MQ-TMR03 Tripod Mount Ring for Canon EF 70-200mm f/4L IS USM, EF 300mm f/2.8L & f/4L, EF 400mm f/2.8L & f/4L Lenses (Black) Professional Grade Improves Tripod-Mounted Lens Balance Simple to Install and to Remove Rotates for Horizontal/Vertical Shooting Thumbscrew Tightens and Loosens Ring