7939WG-WH -  Honeywell Surface Mount Contacts (White)
Traditional 39 style surface mount    All accessories included    Standard gap: 1.0 in. (25mm)This protective device monitors the opening and closure of doors and windows.Alarm Contact switches are magnetic switches used to protect doors and windows for the most part. Doors are the most common place of entry and should be protected by your alarm system. The Home Security Store always recommends contacting every perimeter door in your home or business.