Oil Blocked Flue Safety Switch Kit for Use w/Rear Flue Basement Style Oil Furnaces, Designed to Detect a Blocked Vent System, Responds to Hot Flue Gases Backing Up Through Its Heat Transfer Tube, and is Designed to be Wired to Shut Off The Oil Burner, Kit Includes: 1 Switch, 1 Wire Harness w/72" Long Bx Cable, 2 Insulated Male Connectors, 2 Insulated Female Connectors, 4 Self Tapping Screws, 2 P-Clamps, 2 Wire Nuts and Installation Instructions, In Mfg Box, Made In USA.