Lock Ring for Canon EF 600mm f/4L IS III USM lens.

A lock ring is included with every lens hood order if required by the lens hood.
Lock Ring for Canon EF 600mm f/4L IS III USM lens. Compatible with Zemlin Photo HZ-160 & HZ-S158 Series Hoods. Approximate weight: 42g. Order only as a replacement or if using a hood on multiple lenses.  Photo shows an older 600mm lens which takes a similar ring.