Simplify power transistor mountings and insulation, and improve thermal efficiency with molded insulators. These insulators are molded of Type 6/6 Nylon for regular applications and molded of Glass Filled Polyester for heavy duty uses. They replace up to six pieces of conventional insulation required with previous mountings. They also increase the amount of interface surface between device and sink by minimizing clearance holes required for all feed-thru connectors. They also have a built-in barrier which not only eliminates need for sleeving of base and emitter connections, but also serves as an assembly aid during installation.