The Duclos Lenses 80mm Front Rings are designed to provide a smooth, flat, 80mm outside diameter surface for mounting common accessories such as matte boxes or filter trays to your lens. Made of solid billet aluminum and anodized black, all of the Duclos Lenses 80mm step-up rings also feature an inside thread of 77mm for attaching common 77mm filters or other screw-in accessories. A quick upgrade that adds functionality and convenience to any cinema set-up. Available in a variety of sizes to step-up or step-down to a common front diameter throughout your entire set of lenses.
Also, you will probably need an 80mm Front Cap for your new front ring.