Serving as a slimmer alternative to the manufacturer's original lens cover, the ASCC-5 Soft Cap from AquaTech is compatible with the Canon EF 500mm f/4L IS USM and EF 500mm f/4L IS II USM lenses. It protects the front element from dust, dirt, and scratches when the lens is not in use. The cap is crafted from waterproof, flexible silicone rubber, and fits snugly on the end of the lens without touching the front element's surface. Additionally, it can be used in conjunction with AquaTech's SoftHood collapsible fabric hood.