Pack of 10 each Keratherm 86/37 Green TO-3 thermal transistor insulators. Place the pad between your transistor and heat sink to efficiently dissipate heat away from the transistor. Keratherm 86/37 Green is a specially filled silicone elastomer film that offers outstanding thermal conductivity of 1.8W/mK and good electrical insulation properties. Because of its structure, Keratherm 86/37 Greenk, has good self-adhesion with no shelf life. Dimensions are 42mm X 29mm and 0.225mm thick and will fit TO-3 transistor packages. See drawing for hole dimensions to confirm this will fit your application. MFG C of C not provided with order.