Keep unwanted light from hitting your lens by using the Flex Lens Shade for Large Lens. Designed for lenses 300mm and longer, the ballistic nylon shade attaches to lenses or hoods via the hook-and-loop fasteners, bending to your needs in order to block light that would otherwise create lens flare.
When you're shooting outdoors it can also act as a shield against rain, dust, and dirt. Not only can the Flex Lens Shade block light, it also has a highly reflective side, so it can attach to a flash and create a bounce for a bigger spread of light. Fold the Flex Lens Shade down over your lens to prevent scratches when not in use, and just lay flat for storage.