To220 bolt on heat sink 21 59mm fins trusemi bk t220 0061 to220 bolt on heatsink aluminium material black anodized finish 17 c w thermal resistance 17 78mm long 17 8mm wide 21 59mm high black anodised pre drilled heatsink to accept a wide variety of to220 packaged semiconductors i e voltage regulators and power transistors may be mounted horizontally or vertically trusemi bk t220 0061 to220 bolt on heatsink