Twin Hornet heaters are the only DUAL COMPONENT heaters on the market. There are two fans, heating modules, and thermostats, all in one housing. This design provides TWICE the protection of other heaters because when a part fails (every heater made will eventually have a part fail) the heater will still protect your engine. It is certified safe as required by the U.S. Coast Guard for use in areas that may contain explosive gases like a bilge or engine compartment. We use a patented Stainless Steel heating module that is self temperature regulating, it is the newest and safest heating module you can buy and it can not overheat. This allows us to offer a heater with the smallest footprint on the market. The fans are 40,000+ hour, long life, brush-less, ball bearing type that are manufactured to our stringent requirements. The thermostats are hermetically sealed and turn the unit on at 40ºF and off at 46ºF, this is the tightest temperature differential on the market and it will consume 36% less electricity than heaters that heat to 55ºF! The 25' power cord is rated to -20ºF and for wet locations. Certifications: ISO 8846, SAEJ1147, IPX7 means your heater is certified to operate in an area where combustible gases may be present. Ours is also the only WATERPROOF bilge heater, competing units are only water resistant, there is no comparison between the two ratings.