The Wamu 70000 series of boxcars held a gross of 15 tons and a net of 10.3, making them more productive than the Micro Ace A3031 Temu 300 Steel Closed Wagon (Boxcar) which also grossed out at 15 tons, but only carried 9.2 tons. 

While these are the same cars as the MicroAce MA A3051 units, the reporting numbers are changed to 74354 and 74200 and striking yellow stripes indicating express status have been added.