Schlage Double Cylinder Deadbolt. B-series double cylinder deadbolt for exterior doors. Grade 1 security. Features Snap-And-Stay hands-free installation. Deadbolt locked or unlocked by key from exterior or interior. Dual option latch includes: 1/4" round corner and 1" circular drive-in latch, adjustable backsets. Strike: 1/4" round corner full-lip strike. Meets BHMA (Builders Hardware Manufacturers Association) standards. Grade 1 door prep required for latch bolt while 2-1/8" required for deadbolt cross bore.