The first models of the tank destroyer were tested by the US Army's 704th Tank Destroyer Battalion. The unit had originally been trained on the M3 Gun Motor Carriage (a 75 mm gun installed in the bed of an M3 half-track). Despite its T70 prototypes requiring several improvements, the 704th had a "superlative" testing record, and the unit was later issued production Hellcats after many of their suggestions were integrated into the vehicle. The testing phase of the Hellcat proved that teamwork was an essential element of the new light tank destroyer units, and replaced the fixed, rigid structure of other units with a much more flexible command structure that allowed adapting to more complicated tasks.