This lens hood is designed specifically to fit the Canon EF 400mm f/2.8L IS III USM. It prevents stray light from entering the lens which can be a source of flare and ghosting and also provides a degree of protection for the lenss front element. Its built to the same exacting standards as the 400mm f/2.8L IS III USM, designed to blend in perfectly with the lenss thermally insulating white paint exterior. Benefits Prevents flare and ghosting when shooting into the light Protects the lens front element from accidental damage Designed specifically for the EF 400mm f/2.8L IS III USM Styled to match the white exterior of Canons super-telephoto lenses Lightweight, weighing just 270g (approx.) Can be reversed and attached to the lens to save space What\'s in the box Canon ET-155 (WIII) Lens Hood Compatibility EF 400mm f/2.8L IS II USM EF 400mm f/2.8L IS III USM RF 400mm F2.8L IS USM RF 800mm F5.6L IS USM