53-77-9G is a Thermalsil III thermally conductive silicone rubber insulator designed for TO-220 package devices. It features dimensions of 18.42mm x 13.21mm (A x B) with mounting hole specifications of 4.32mm (C) and 2.92mm (D), and a thickness of 0.152mm (0.006"). The insulator is composed of silicone elastomer binder with thermally conductive filler, reinforced with glass cloth to resist tearing and cut-through from burrs on transistors or heat sinks. With a thermal conductivity of 0.92 W/m°C and dielectric breakdown voltage of 26.3 x 10³ volts/mm, it provides excellent electrical isolation while maintaining efficient heat transfer. This RoHS compliant insulator eliminates the need for grease application and is ideal for power semiconductor mounting applications requiring both thermal management and electrical isolation.