Compatible with VX-5HD VX-6 and VX-6HD riflescopes with 42mm Objective lenses. Not Compatible with M8 and FX-3 42mm riflescopes. Designed for Leupold scopes built after 2004 Alumina® Flip-Back™ lens covers feature powerful neodymium magnets to hold them securely closed and the triple O-ring seals 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 be rotated so they can open in any direction.