Permatex Sensor-Safe Blue RTV Silicone Gasket is a single-component, room-temperature vulcanizing (RTV) gasketing compound. It's designed to create reliable "formed-in-place" gaskets for mechanical assemblies. This silicone rubber cures upon exposure to air moisture, forming a tough, flexible gasket. It's resistant to aging, weathering, and thermal cycling, and it won't harden, shrink, or crack. This is the original "Blue" gasketing product, now refined and safe for use with oxygen sensors.