Weiser's SmartKey re-key technology provides you the flexibility to re-key your locks quickly and easily without removing them from your door. Plus SmartKey cylinders represent a quantum leap in security as compared to traditional pin- and-tumbler cylinders. The lock cylinder uses two steel balls inserted into the front of the key face to resist attack from drilling. This satin nickel Phoenix lock works with door thickness: 1-3/8" - 1-3/4". Both knobs are locked or unlocked by key outside or turn button inside.