4xAA batteries for stable battery life, low battery voice system reminds to replace the battery(Note: Batteries not included) Automatic lock when closing the door, magnetic lock, the door tongue senses the magnetic stone and automatically locks Unlock via mobile app: without holes, single-sided installation without holes indoors, no traces outdoors Widely used: Indoor non-metal door locks for homes, offices, etc., door thickness does not exceed 60mm, Manufacturer: Akfldms