Lens hoods are primarily designed to avoid 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.

LH-2 replaces : for NIKON HR-2 Screw-in Rubber Lens Hood

Compatible models :

for NIKON 50mm f/1.2 AI-S

for NIKON 50mm f/1.4, 1.8 D-AF

for NIKON 58mm f/1.2 Noct AI-S Lenses