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 also get the added benefit of some extra protection from accidental impact.

Dedicated lens hoods are designed to match the specific focal length of the lens it was designed for.

Usable EF Lenses:
EF 85mm F1.8 USM
EF 100mm F2 USM
EF 135mm F2.8 Softfocus
EF75-300mm f4-5.6
EF100-300MM F4.5-5.6 USM