This aluminum tripod collar mount ring is specially designed for Canon EF 70-300mm f/4-5.6L IS USM, balancing the lens & the camera, making it more convenient for you to adjust the lens after fixing on tripod. Ring inner diameter: 81.5mm, Ring width: 18mm, Ring thickness: 4.5 ~ 8mm, Color: White. Just spin the knob & pull it out, you can release the ring. Specifications: Material: Aluminum Compatibility: For Canon EF 70-300mm f/4-5.6L IS USM Ring Inner Diameter: 81.5mm Ring Width: 18mm Ring Thickness: 4.5 ~ 8mm Item Weight: 161g / 5.7oz Package Size: 14.2 * 9 * 8cm / 5.6 * 3.5 * 3.1in Package Weight: 230.5g / 8.1oz Package List: 1 * Tripod Collar Mount Ring