Do you have an older door with smaller than standard door prep? The most common door prep is 2 1/8" dia. You probably know this already and have been looking all over for something that will fit a 1 5/8" dia. bore hole. We now carry Baldwin door hardware and they make a deadbolt that will work on this smaller sized bore hole. Check it out: Baldwin Deadbolt for 1 5/8" dia. bore hole. Baldwin Single Cylinder Deadbolt for 1 5/8 Inch Dia. Bore Hole