The Pipe Car No. 6121 was available in 1956 and 1957, and was created on a stamped steel chassis. Early cars would have bar-end trucks with magnetic or tabbed couplers, while later editions have early AAR trucks equipped with disc couplers. Came with four to six pipes and these are easily interchangeable with the similar No. 6111 log car.

There are five variations to this car that have to do with the trucks that were used and the color of the car. These cars were available in DARK GRAY (A Variation), CREAM (B Variation), YELLOW with bar-end trucks and serif lettering (C Variation), BRIGHT RED with serif lettering (D Variation) and YELLOW with early AAR trucks (E Variation).