The Ikelite SLR Zoom Sleeve For SIGMA 8-16mm F4.5-5.6 DC HSM Lens works with the Black Housing Gear to enable you to operate the zoom on your SIGMA 8-16mm F4.5-5.6 DC HSM lens while it is installed in the Ikelite housing. It fits over the lens and has teeth that align with those of the housing gear.