After-sales service: Providing customer service that responds within 24 hours. If you have any questions about our door locks, please do not hesitate to contact us, we offer 365 days after-sales service.Warm Tips: The fingerprint doorknob requires 4 AAA batteries (not included), which can be used for up to 8-10 months depending on the frequency of use. Low battery reminder function (the red light flashes three times when unlocking); equipped with a USB interface, which can be used for backup power.Easy Installation: Keyless door lock is designed to fit American standard door, Backset 2-3/8″(60mm) and 2-1/8″(70mm), door thicknesses from 1-3/8' to 2-1/8'(30mm -55mm). The lock installs quickly and easily with just a small screwdriver. Fits both left and right-hung doors (suitable for indoor and outdoor doors).Multiple Access Methods: 4-in-1 biometric door lock meets daily life. Code unlocking, 4*key fobs and fingerprint unlocking - no need to carry keys or worry about looking for keys everywhere. Mechanical key can be used as a backup key to unlock (in case of emergency such as dead battery).Fingerprint Sensor: 508 DPI fingerprint sensor module, 360° fingerprint reading is accurate and fast, supports storing up to 100 sets of fingerprints, and the recognition rate exceeds 99% within 0.3 seconds.