F.A.S.T. = Fully Articulated Suspension Technology refers to hip rings. Hip rings help with extreme leg positions in freefall and when you are stuffing big guys in small airplanes. Multi-Flex harnesses have hip and chest rings. Chest rings allow you to crank the chest strap really tight. This helps keep the shoulder straps where they belong during head-down freefall. Both terms were coined by Rigging Innovations, the company that invented ringed harnesses.