Contemporary Round deadbolt double cylinder ultramax security clear pack adjustable with a polished chrome finish. Double cylinder deadbolt with smart key rekeying, grade 1, round corner adjustable latch fits 2-3/8 inch and 2-3/4 inch backsets, ball bearings to prevent drill out, concealed screws, keyed alike in sets of 4, lifetime mechanical warranty, lifetime finish warranty, clear pack. Operated by key on both sides. Signature series' deadbolts feature titanium alloy throwbolt core and ultra-strike for jamb brace. This design includes"bumpguard" for improved security against lock bumping. Door prep: 2-1/8 inch or 1-1/2 inch cross bore, 1 inch edge bore, 1 inch x 2-1/4 inch latch face. Door thickness: 1-3/4 inch. Includes 3 anti-pick top pins. Faceplates: 1 inch x 2-1/4 inch round corner. Strikes: 1-1/8 inch x 2-3/4 inch round corner. Includes ultra-strike door jamb brace with (3) 3 inch screws. Bolt: Brass bolt, full 1 inch throw. Titanium alloy throwbolt core. Ansi/bhma: Grade 1. Deadbolts with"smartkey" (denoted smt) feature allow, in 3 steps, locks to be re-keyed to a spare set of keys. When the spare keys are done being used, the lock can be re-keyed back to the original set of keys; can continually be re-keyed.