The double cylinder deadbolt from Stone Harbor is the complete package, giving you both style and security. Function (Double-Cylinder): Double cylinder handlesets and deadbolts are operated solely by a key on both the exterior and interior. Since you will not be able to unlock this from the inside without a key, please make sure your intended usage follows the local fire code before purchasing. Comes standard with round corner, square corner and drive-in faceplates. Backset is adjustable from 2 3/8 inches to 2 3/4 inches. Fits doors from 1 3/8 inches to 1 3/4 inches. Includes a 1-inch by 2 1/4-inch round corner strike. Meets A156.2 ANSI/BHMA Grade 3 requirements. Choice of keyway, for more information refer to our FAQ. HL010104