Prime-Line E 2294 Vintage Style Mortise Lock Assembly, 5-1/2 in. Face Plate, Brass Plated Steel This mortise caselock is used indoors with old style mortise lock sets 2-3/8 in. backset with a 9/32 in. square spindle drive accepts a max. spindle size of 1/4 inch Brass plated finish Constructed of steel and diecast components