TO-3 /TO-220/TO-3P Transistor Insulator Set with Bushing/Washer

Silicone/Mica: 0.2mm. Thickness: Alumina - 0.8mm (T hermal conductivity (30 W/mK )). Size : 19mm, 13mm. Material: Silicone/Mica /Alumina (Aluminium Oxide).

eBay