All serie 60 Balmar alternators have the following characteristics: dual internal fan; high output at low speeds; heavy-duty oversized bearing; meet the USCG standard for marine use; white ''powdercoat'' finish; corrosion and spark proof; Smart regulator or external regulators; proved in marine and military use; made in USA with a 1 year warranty; max speed: 10 000 RPM. Type #621 is the most common in North America: one 1'' leg (Motorola Style), with spacer to create one 2'' leg (Delco Style). 100A output. Optional external regulators are sold separately.