Canon lens hoods are one of the most important accessories for each lens you own.
A lens hood provides multiple functions: it shades the lens from stray light,
improving your contrast and image quality; in inclement weather, it can assist
in keeping moisture or wind-blown debris off the lens; and it protects the front
barrel from the inevitable impacts against walls, door frames, and other real-life
obstacles. Almost all EF and TS-E lenses have a Canon lens hood engineered specifically
for it.
For Canon EF 20mm f/2.8 USM.