Focus gears allow access to the mechanical zoom function of many lenses. Use of these gears may require specific port extensions and may not be available for all housings and lenses.
This focus gear is specific for the Nikon AF-S NIKKOR 16-35mm f/4G ED VR lens.
This focus gear is great for supermacro shots with the Canon 100mm F2.8L IS USM lens, especially when used with a wet diopter. This gear is for the "L" version of the lens only.