Some collared, telephoto lenses have a foot than can be removed. If your lens has this option, choose one of our foot replacements instead of a lens plate. A replacement foot with built-in-dovetail mounting will be lighter, lower in profile, and provide the best possible stability for your lens. Really Right Stuff foot replacements are precision machined from solid blocks of 6061-T6 aluminum and are fully compatible with 1.5" RRS Dovetail Standard. This foot replaces the Canon foot on the Canon 100-400mm f/ 4.5 - 5.6L IS II USM lens.