The natural evolution of your typical ring grinds (see a tutorial here), the behind-the-back ring grind can make a fabulous close to a ring performance or (with a little more dedication) mix up the pace in the middle of your routine.
Tips/Hints
Stepping back before you throw the blue ring (the one you intend to grind) and stepping forward before you catch can save you a lot of time, because it means all you have to do is throw the ring straight up. Without the footwork you need to throw the ring behind you, making the trick much more difficult.