JJC ET-74B Bayonet Reversible Lens Hood Shade for Canon RF 100-400mm f/5.6-8 is USM and EF 70-300mm f/4-5.6 is II USM Lenses, Replaces Canon ET-74B Lens Hood, Not Affect to Use 67mm Filter or Cap

Here's a link to it on Amazon. Lens hoods reduce lens flare by blocking stray light, and offer some physical protection against things hitting the glass. https://www.amazon.com/JJC-Bayonet-Dedicated-70-300mm-Replaces/dp/B06XTP2FD3