The ET-73C Lens Hood from Canon is designed for the RF 100mm f/2.8L Macro IS USM Lens and prevents unwanted stray light from entering the lens. It extends the shading at the end of the lens and minimizes ghosting and flare when shooting in strong lighting conditions. Additionally, since the end of the lens is extended, you also get the added benefit of extra protection from bumps and impacts.
Perfect fit for my RF 100mm f/2.8L Macro IS USM. It blocks stray light and reduces flare nicely, and the extra bump protection gives me peace of mind. Solid Canon build—5 stars.