Let's see your iphone cases / back protectors.

Anyone recommend a decent back protector for the iphone 3GS? I don't want a full case just the back part as don't want something the size of a breeze block in my old sky rocket!

I've bought a load of these cheap ones for a couple of quid made of plastic but they all just break either straight away or after a day or two as the plastic cracks around the edges.

I fancy a carbon fibre one but they are about £30 but anyone know how strong they are?

Cheers