Joinwin&reg; Wireless Home Doors Windows Security Entry Alarm System with Magnetic Sensor - EASY to install FREE BATTIRES!! (Pack of 6)(White) Easy to install--just peel and stick Size: 6.2cm x 3.2cm x 2cm Magnetic sensor switch detects entry protecting your home or office 6 pieces Operated by 3pcs of. 5VLR44 / AG 13 button cell ( included )