The 7939WG-GY is a grey, surface mount, magnetic door/window contact designed specifically for residential and commercial use. Working with a 1.25" magnet gap, the 7939WG-GY provides a reliable solution for securing door and window access points. The contact comes with spacers, covers, and screws for fast and easy installation.The 7939WG-GY replaces: ADEMCO PR20439, 7939, 7939W / Aleph DC2541, DC2541-WG / FBII ZR735 / GRI 29A / Intellisense MPS20 / Nascom N-85T / Sentrol 1085T, 1285T / Tane SM35 Also known as -Honeywell Sensors SURF MNT 1-1/ 4 GAP TERM GRAY - 7939WG-GY