The Aqua Tech SoftHood, being light and collapsible and very difficult to damage, is a practical alternative to the originally-supplied metal or carbon fiber hoods that you find with the enormous lenses for SLR cameras.
This particular model fits any 500mm f/4 or 300mm f/2.8 lens; it comes with a pair of compression straps to perfectly affix the SoftHood to the outer diameter of your lens barrel no matter the maker. SoftHood's faster to deploy than a 'reversed' normal hood since you just extend it from its collapsed state, and of course with a name like Aqua Tech it was designed with excellent water resistance in mind.
SoftHood Collapsing Hood for 500mm f/4 & 300mm f/2.8 Lenses
1-Year Limited Warranty Against Manufacturer's Defects