Lock Ring for Canon EF 400mm f/2.8L USM lens.

A lock ring is included with every lens hood order if required by the lens hood.
Lock Ring for Canon EF 400mm f/2.8L USM lens. Compatible with Zemlin Photo HZ-161 Series Hoods. Approximate weight: 50g. Order only as a replacement or if using a hood on multiple lenses.  Photo shows the 600mm lens which takes the same ring.