Designed for Leupold scopes built after 2003, Alumina Flip-Back lens covers feature powerful neodymium magnets to hold them securely closed and triple O-ring seals for provide maximum protection from the elements. The cover opens silently and folds flat against the scope in the open position. Constructed out of durable 6061-T6 aircraft grade aluminum, they are precisely machined to allow for quick and easy operation, and a low-profile position, when open, make these Flip-Back lens covers stand above the rest. The round objective and ocular models can be rotated so they can open in any direction. It fits 40mm.