Just need to screw out the retaining screw with a screwdriver, then dismount the old or broken lock core and replace the new one. Save your money and time. Suitable for metal doors, anti-theft doors, standard doors.Material: MetalColor: as pictureSize: The length and width of the cylinder is about 9*3cmThe key length and width are about 5.5*2cmConversion: 1inch=2.54cm, 1cm=0.393inches Warm Tip : Please be reminded that due lighting effects, monitor\'s brightness/contrast settings etc,there could be some slight differences in the colour tone of the website\'s photo and the actual item. Item Measure by hand, it could be 1cm different,your kind understanding will be much appreciated.