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.   Features: Designed for Canon EF 70-300mm f/4-5.6L IS USM, balance long lens and camera, protect it away from unexpected dropping.  Make it 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.  Made of strong & durable aluminum, fine workmanship ensure perfect conformity in color and surface qualities.  Spin the knob, pull it out to unlock it, tightened locking system.  Soft inner ease the pressure on your valuable lens.  With a 1/4" female screw on the bottom.   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