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