The hands down WORST feature of the Thrustmaster wheels is the "quick release system", which is a giant plastic thread and a screw that takes about 30 seconds to change out a wheel compared to Fanatec's realistic full-metal quick release system.
Even with the screw my wheel would sometimes randomly get loose and it was making me so mad. The giant thread isn't the annoying part of changing wheels, it's the screw that would make the wheel go loose without it. But with this adapter ring, you can tighten down your wheels just that extra bit and it holds your wheels in place beautifully.
In conclusion, this is a must-have accessory if you're buying a T300/TM or other Thrustmaster wheel base with the same giant plastic "quick release system". It's cheap and is SO helpful.