The Army Combat Shirt (ACS) is a flame-resistant shirt developed and used by the United States Army as a supplementary addition to the Army Combat Uniform. The ACS is a stand-alone shirt designed specifically for use with Improved Outer Tactical Vest armor in warm and hot weather instead of the blouse. It is intended to greatly increase user comfort through the use of lightweight, moisture-wicking, and breathable fabrics. The ACS was created in conjunction with the USMC's Flame Resistant Organizational Gear (FROG). The ACS, in conjunction with the Fire Resistant ACU (FRACU) trousers, provides head-to-toe protection against burns.