nickel gold plated for durability to provide nestling for high power rf and microwave flange packaged transistors and diodes in accordance with the present invention transistor and diode carrier modules have a common rectangular shape with common outside dimensions the only difference is that the cavity at the center of each module is carved or otherwise formed to match a specific package style the transistor or diode module has a corner notch that allows it to be placed in only one position inside the heat sink center cavity each module also has four recessed screw holes on the surface of the module and two screw holes inside its center cavity which match with the screw hole positions of the specific package it is designed to nestle and which allow the packaged transistor or diode to be screwed down to the carrier module if needed when the carrier module is placed inside the center cavity of the mounting shelf heat sink the screw holes of the carrier module line up with the screw holes of the center cavity of the mounting shelf heat sink when testing a high power packaged transistor or diode the appropriate carrier module having a matching cavity geometry with that of the packaged transistor or diode under test is first installed in the heat sink cavity and bolted down to the heat sink for maximum heat transfer once bolted down inside the.