Canon ET-65B Lens Hood Compatible with 70-300mm f/4.5-5.6 DO IS & f/4-5.6 IS USM Lenses - Durable Camera Accessory for Outdoor Photography and Travel

The Canon ET-65B Lens Hood, as with other lens hoods, is made to keep undesired side lighting from entering the lens.  It does this by extending and shading the end of the lens. Furthermore, since hood extends from the lens, it gives extra protection from accidental impact.  It is removable and attachable in reverse to take up as little space as possible when storing in camera bag.