I think most guys go off the # connections of the arms rather than if it is a radius arms or not, To make it really easy if there is no upper arms or the uppers connect to the the lowers it is a radius setup if the upper have their own mount then it is a a " True 4-link or 3-link". IRO uses a Y radius arm that connects to the upper and lower axle mounts, for what they call a 3-link long arm kit.