The Dedicated Lens Hood (Lens Shade) for 25mm f/2 Lens from ZEISS is specifically designed for use with the Distagon T* 25mm f/2.0 ZE Lens for Canon EF Mount and the Distagon T* 25mm f/2.0 ZF.2 Lens for Nikon F Mount.

Lens hoods are primarily designed to prevent unwanted stray light from entering the lens by extending and shading the end of the lens. In addition, since the end of the lens is extended, you get the added benefit of protection for the lens from accidental impact. This dedicated lens hood is designed to match the specific focal length of the lens it was designed for, long enough to deflect sufficient light without extending into the field of view.