Aavid thermalloy 6398b 4 4 c w bolt on heat sink for to 218 to 220 aavid thermalloy 6398b a high power extruded bolt on heat sink with large radial fins and straight pins suitable for use with to 218 and to 220 type components aavid thermalloy 6398b heat sink for to218 and to220 4 4 c w bolt on type