This item is New & unused, box has been opened to check contents only. Easy installation on your home door without any construction work. Your smartphone is the key to your home. Don’t forget to lock the key with the auto lock function. Batteries can operate for up to 600 days (when 4 batteries are inserted, 2 batteries are included). You can insert 4 batteries, but it will be driven by 2 batteries to notify you that the battery is dead. 4.55 x 2.24 x 3.33 inches. 2 Lithium Metal batteries required. Keyless Smart Door Lock. App Compatibility, Smartphone Compatibility. Balcony/Terrace Door Barn Door Bathroom Door Bi-Fold Door Cellar Door Closet Door Commercial Door Fitting Double Door Entire Door Fire Door Folding Door French Door Front Door Front Entrance Door Hidden Door Interior/Room Door Mirrored Door Panel Door Patio Door Pocket Door Prehung Door Residential Room/Pass Door Saloon Door Security Door Side Entrance Door/Backdoor Slab Door Swinging Door. Borg & Beck BBD4640 Brake Disc Pair (Front).