Alumina Flip Back Lens Cover Kit6061 T6 aircraft grade aluminum For Post 2004 Riflescopes Leupold's? Alumina Flip Back Lens Cover Set? allows you to keep your riflescope's standard eyepiece and 40mm objective lenses protected from dirt, rain, and other common trail hazards with internal springs that allow each cover to be quickly flipped out of the way when you need to use the scope. Made of lightweight and durable 6061 T6 aluminum with a matte black anodized finish, the covers