A “super-sized version of the original”, the Montana Magnum Hadley eyedisc, has an eyedisc diameter of 1.95″ and 15 apertures ranging in size from .021″ to .115″. The Magnum features the same O-ring found on the standard eyedisc. In addition to the larger apertures, and the rubber O-ring, the larger eyecup actually blocks out unwanted light from around your eye, which creates a brighter image through the aperture. During low light conditions, this eyedisc delivers a competitive advantage by allowing the shooter to continue opening up the aperture until a crisp sight picture is seen clearly. 10-40 threads fit MVA Soule sights.