This product is a thermally conductive silicone pad for transistor / mosfet packages - TO-247, TO-248, TO-218, TO-3P and SOT93 cases. 0.4K/W, 24x20mm (Height x Width). This item is also referred to as heatsink insulation pad and made of thermally conductive silicone can be used with or without thermal grease / heatsink compound.