Battery Powered Window, Door and Cabinet Alarm - Easy to Install (Pack of 4) Alert systems lets you know if an interior or exterior doors, windows and cabinet doors has been opened Three 1.5V button cell batteries, INCLUDED Easy tool-free installation to window or door; Mounted using double-sided adhesive tape or glue (included) Pack of 4 sensors for four windows or doors 90 DP plus @ 3 ft. sound level