Use this Sea & Sea 31121 Zoom Gear to control manual zooming with your Nikon AF-S DX NIKKOR 10-24mm f/3.5-4.5G ED lens in a compatible lens port, which mounts onto an MDX or RDX underwater camera housing. Manual focus cannot be used when this zoom gear is in place. The gear mounts onto the zoom ring of the lens and is controlled via the focus/zoom dial/knob on the housing. It is constructed from a corrosion-resistant aluminum alloy.