Fizik Antares Versus X Chroma SE Matte Black with Kium Rails QBP Exclusive Nylon carbon-reinforced base with up to 20mm deep pressure relief channel Thermo-welded cover provides flat transition between different panels Wing Flex shell flexes downward where the inner thigh contacts the saddle allowing more efficient Kium Rail: special alloy with a high strength-to-weight ratio and excellent vibration damping (8% Nylon carbon-reinforced base with up to 20mm deep pressure relief channel