Catalog > Electro-Mechanical Components > Fasteners Hardware > Electronic Hardware > Heatsink Insulators and Bushes Silicone Rubber Thermal Insulator Silicone / Rubber / Thermal Insulator Silicone Rubber Thermal Insulator Part No: TO-3 3.74 ZAR inc for 1 Each (Quoting) Add to Cart Specifications, Prices & Availability may change without notice. Images are for illustration purposes only. E&OE Overview This silicon insulator is designed to be mounted between transistor and heat sink with good thermal conductivity and insulation.