Camo Neoprene Cover.
Lenscoat part number TC40056DC.
The TravelCoat for the Canon 400mm f/5.6L AF Lens from LensCoat in Digital Camo is a 3.0mm thick, shock-absorbing 100% closed-cell neoprene lens cover that is custom-tailored to fit your lens. It is designed to fully protect the lens when not in use, without the need for a more comprehensive lens case and allows more valuable room for packing and storage. The coat slides easily over the lens, and closes with a secure hook-and-loop closure.