 Key parts of the specification included adjustable-gauge trucks, compact bodywork to fit restrictive loading gauges and structure gauges, replaceable couplers to fit a variety of systems, and a power output of .The trucks' wheelsets adjusted between standard gauge () and Indian gauge (), which encompasses the vast majority of the broad gauges in use worldwide, including those of the then Soviet Union ( ) and of the Iberian peninsula (Iberian gauge ).The specification was put out to tender, and two companies responded; GM and GE.