77mm Pro Series Snap On Lens Cap for Sigma 10-20mm f/4-5.6 EX DC HSM Autofocus Lens, Sigma Normal 50mm f/1.4 EX DG HSM Autofocus Lens, Sigma 70-200mm f/2.8 EX DG APO OS HSM & Many More Models This lens cap protects lens surface from dust & shock during storage. Unique snap on design allows easy installation onto the lens & one-step removal from the lens. It fits directly onto the lens with a double-action spring design. Microfiber Cloth 77mm Snap On Lens Cap