Engineered Garments C 1 VEST HBX HYPEBEAST C 1 Vest U.S. Armed Forces Army Air Force C 1 Emergency Vest eBay Thrifted a Type C 1 Emergency Vest. Is this real? : r Militariacollecting. The C 1 Vest is a versatile, mid weight piece made from a durable cotton poly twill fabric, designed for a standard fit. Crafted in the USA, it features a V neckline, front button and tie closure, angled flap cargo pockets on the chest and waist, a lower back cargo pocket, and a unique back cut out with self tie fastenings. Perfect for layering or adding an extra edge to your look.