WAFU Invisible Keyless Wireless Remote Control Electronic Lock Features: Made of good quality zinc alloy and stable performance. Invisible remote control lock, specially designed for home security. No keyholes outside, there is no way for thieves. Tiger lock method, more safe and stable. Super design and easy for installation. Specification: Host Machine: Material: Zinc Alloy Size: 15.5 * 8 * 3.5cm Power Supply: 2 * AA batteries(not included) Transmission Frequency: 433MHz（±500KHz） Operation Range: Within 20m Unlock Mode: Remote control unlock& Mobile Phone Unlocking (additional Bluetooth adapter is required) Remote Controller: Color:Silver Size(Each): 6 * 3 * 1cm Battery(Each): 1 * CR2032 3V(Included) Standard Number: 4 (included) Maximum Controller Number: 16 (not included) Function: Lock & Unlock Package List: 1 * Lock(Not included batteries) 1 * Lock Body Holder 1 * Lock Catch 4 * Remote controller(Built-in batteries) 1 * Bag of Mounting Screws 1 * USB Cable 3 * Fixed Sticker 1 * Manual Note:The device beeps and flashes a red light to indicate low battery. If the battery is too low, it cannot be locked and needs to be replaced with a new battery.