Typically though of as the goo used in compression and split-bolt connections where aluminum wire is used, the PENETROX product is an oxide-inhibiting grease designed to create an air-tight and moisture resistant joint. The goal is to prevent the oxidation or corrosion of the metal products used in the electrical connection. Depending upon the type of metals found in the joint, you would use a specific version of the product containing suspended particles designed for that metal. Type "A" contains Copper particles and is used for Aluminum to Copper or Aluminum to Conduit (Steel). Type "B" contains Zinc particles and is used where the metals are all aluminum. It has found favor in a number of industries, such as Ham Radio operators, where the grease acts as a lubricant for threaded connections and reduces the chance of them seizing down the road.