For residential single and multi-family hall/closet doors. Both knobs always unlocked. 1 piece knob for better appearance. Solid brass trim and all metal parts. 3 piece assembly for easy installation. DUAL OPTION UNIVERSAL: Fits all doors, 2-3/4" or 2-3/8" backset; 1-1/8" square corner, 1/4" round corner, or circular drive-in preps