I posted something a while back about these, but they finally came the other day.
The are the absolute dogs, look nice in Aluminium with blue flashes.
You can tighten them so far by hand, but have to use a special key to tighten them.
There is two small round holes in the top the key fit's into.
Once tightened, the outer edge just spins round and round.
There is no way you could get them off without the speciall tool.
They even give you two removal tools on keyrings as well.
They cost me £12.94 for two sets, making them £6.50 each which is a steal.
Check them out at www.spin-caps.com