Internally there is an efficient heat sync, solid component mounting and it's all encased in a clear epoxy. - Must be used with HVC Coil PN 8250. Part #: 6631. Product Line: MSD. Holley, Holley EFI, Aeroflow, Aeromotive, B&M, MSD, Brawler, Hooker, Hurst, Mr Gasket, MSD Dynaforce, NOS, Quick Fuel Technology, Racepak, Spal Fans, Weiand, Jesel, Wilson Manifolds, Competition Cams, Crower Lifters, Johnson Lifters, Daimond Pistons, CP Pistons, CP Carrillo, RCD, GRP, Dailey Engineering, Manton Pushrods.