An Aquatica Focus Knob gives you the perfect control you need when performing that critical focus. It also makes it easier to zoom with a wide angle lens. The Focus Knob presses onto your existing knob, vinyl tape is included to ensure a snug fit. A spacer and hardware are included to give you more room to use the focus knob (for the 1DS MkIII Housing). The focus knob and handle spacer are constructed of durable Red plastic.