Alumina Flip-Back Lens Cover 50mm.

From the Manufacturer:

Compatible with Leupold® post-2004 riflescopes with 50mm objective lenses, except for VX®-L and VX®-3L models.

Our Alumina® Flip-Back™ lens covers feature powerful neodymium magnets to hold them securely closed, and triple O-ring seals to provide maximum protection from the elements. 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 rotate so that they can open in any direction.