Little is known about the Equestrian secret military uniform: class C. Often “worn” by tank crews due to the tight, hot environments they work in. It is often preferred by many units in the field, who often do maneuvers. It has been rumored that even a few tank crews wear class C into battle! While its been unproven, tank commanders believe class C allows their crew to ‘remove barriers, bond better with each other, and learn deeply about their crew members’.
 
Original: Link  
Post card: Link  
Class-C post card (NSFW): Link