Steam Heater Cars, known in Canada as Steam Generator Units or SGUs, were introduced in the diesel era to provide steam heat to passenger trains in cooler weather. When passenger trains were hauled by steam locomotives, there was always a reliable source of steam. Unless a diesel locomotive was equipped with a boiler and water tank, heat could not be provided. This was before the days of electrical Head End Power for passenger cars. Heater cars were frequently rebuilt from boxcars, B-units and old steam locomotive tenders, so they varied in shape and size from railroad to railroad. That is, unless you are in Canada. It is so cold here so much of the time that purpose-built SGUs were built by CC&F (Canadian Car & Foundry), GMD (General Motors Diesel Division) and NSC (National Steel Car). Our model is based on the GMD prototype. Check out the usual insane amount of underbody detail!