Performance complies with ANSI (American National Standards Institute) A156.5, Series 4000. UL (Underwriters' Laboratories) rated. 3 hour fire door. Door range: 1-3/8" - 2". Adjustable backset. Square corner, T-strike. Door frame strike reinforcer with 3" screws. 7/8" wrought brass trim ring. Both knobs always unlocked.