From the ManufacturerThe TR-1II Tripod Mount Ring is specially designed for select Canon lenses. The ring is secured around your lens and can be attached to a tripod or monopod via the 1/4"-20 tripod socket on the bottom. It can provide greater stability and balance when working with the heavy tele lens and shooting at the top of your tripod or monopod. Made of premium ABS material, this Tripod Mount Ring is sturdy and durable. The silicone pad on the inside also can protect your lens from unwanted scratches. TR-1II replaces Canon A-2 and AII (WII) Tripod Mount Ring.
Compatibility: Replaces Canon A-2 and AII (WII) Tripod Mount Ring Compatible with Canon EF 70-200mm f/4L lens Canon EF 70-200mm f/4L IS lens Canon EF 70-200mm f/4L IS II USM lens