Abstract: The present disclosure relates to a backset-adjustable latch bolt mechanism of a cylinder lock, more particularly to a latch bolt mechanism so mechanically structured that two options of backset of either 23/8" (60 mm) or 23/4" (70 mm) are alternately available by removing the connecting pin off the retractor slide and pressing down the emerging spot of the fixing button, which is based on a spiral spring, then outwardly pulling the extension case, letting the spot of the case fixing button pop out in the second bore on the extention case so to change the backset of the latch from 23/8" (60 mm) to 23/4" (70 mm). The latch bolt mechanism is based on a retractor slide having two consecutive latch releasing notches for effecting the mechanical operation.