Entry Sensor For Siren 3Receive Instant Notifications If There Is Unauthorized Entry On The Boat Perfect For Securing Lockers, Doors, And Hatches Install The Wireless Module On One Side Of The Door Or Locker And The Openclose Magnet On The Other Side Link To The Siren 3 Pro And Receive Alerts When The Door Or Locker Is Opened Or Closedfeatures: Compatible With Siren 3 Pro Onlyincludes Wireless Sensor Module And Openclose Magnet