Nikon HB-32 Lens Hood (Bayonet) for 18-105mm DX, 18-135mm DX & 18-70mm f/3.5-4.6G Lens.
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.
Reviews Nikon HB-32 Lens Hood (Bayonet) for Nikon 18-140mm f/3.5-5.6G ED VR, 18-135mm f/3.5-5.6G ED VR, 18-105mm f/3.5-5.6G ED VR and 18-70mm f/3.5-4.5G IF-ED Lenses