Also, the green-blue shoes charge per-step, but the blue-green shoes are billed monthly by signing up for BlueGreenPro+ or BlueGreenMax+, each with a hidden step limit but BlueGreenMax+ is the one that gives you access to the Cyan step model which is better; plus the green-blue shoes are only useful when sprinting, but the blue-green shoes can be used in many different events, but only through the Nike blue-green API that only some track&field venues have adopted...