49MM Lens Hood is primarily designed to prevent unwanted stray light (flare) 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. Screw-mount lens hoods, such as this 49mm, are designed to screw right into your lens or filter. Rear locking ring allows the user to rotate the hood in 360°direction.