Question: do you wear a shirt under a combat shirt

Answer: No, The ACS is constructed of three flame-resistant performance fabrics proprietary to TenCate Protective Fabrics or Massif Mountain Gear Company. The shirt's torso is constructed of two highly breathable flame-resistant fabrics with advanced moisture management capabilities. Both fabrics wick moisture away from the skin and dry rapidly, preventing the fabrics from sticking to the user's skin and greatly increasing comfort under body armor. The sleeves and side panels of the shirt are constructed of a lightweight, but durable and abrasion-resistant fabric designed to provide extra protection for areas not protected by body armor. All three fabrics feature 4-way stretch for enhanced performance and user comfort.