Lock Ring for Canon EF 300mm f/2.8 L USM lens.

A lock ring is included with every lens hood order if required by the lens hood.
Lock Ring for Canon EF 300mm f/2.8 L USM lens. Compatible with Zemlin Photo HZ-118 & HZ-120 Series Hoods. Approximate weight: 34g. Order only as a replacement or if using a hood on multiple lenses.  Photo shows a newer 300mm lens which takes a similar ring.