Single-cylinder. Key outside, thumb turn inside. For 1-1/8" to 2-1/4" thick doors opening in. Latchbolt: 17/32" throw, high-density rust-resistant alloy, brass finish. Latchbolt held retracted and deadlocked by button. Case 3-5/8" x 2-1/2". US5 finish. Backset: 2-3/8".