Performance complies with ANSI (American National Standards Institute) A156.5, Series 4000. UL (Underwriters' Laboratories) rated. 3 hour fire door. 6 pin solid brass cylinder. Adjustable backset. 1-1/8" x 2-3/4" Square corner, T-strike. Door frame strike reinforcer with 3" screws. 7/8" wrought brass trim ring. Push-button locking. Can be opened from outside with small circular tool. Turning inside knob releases button.