This unique product is the most versatile locking unit available, accommodating 7 different hole spacing patterns ranging from 2-11/16 inches to 6-7/8 inches. The 3-15/16-inch hole spacing is specifically designed for use with mortise lock installations, including Adam Rite and W & F mortise locks. These holes are offset by 1/8 inch from the locking cylinder hole, allowing the unit to adapt to a variety of handle sets.