... heat dissipation with serried fins because of a large surface.Compared with extrusion heatsink, usually,with same external sizes ... IGBT) cooling of UPS,Inverter,AC drivers and Transducer etc.Surface treatment: anodized (black),powder coated,polished,mill finished,sand ... better thermal conductivity; so again, a compromise between high surface (many thin fins) and good thermal transfer (thicker fins) must ...