This Cavision 72-77mm Step-Up Ring enables the use of 77mm threaded filters on lenses with 72mm filter threads. The 6mm depth of this ring provides more surface area than a standard step-up ring. This provides a more secure grip to the clamp of your Cavision Clamp-On Matte Box. The step-up ring has a 80mm outside diameter for use with clip-on matte boxes. It features a lightweight aluminum alloy construction with a black anodized finish.