Be careful when buying on E Bay etc there has been a lot of GRP with a carbon look topskin around for a while sold under many guises, I found out the hard way.
Sandbar Composites are very good quality and are sourced from the same manufacturer that makes OEM material for Ducati, BMW etc.
The fit is also much better than with other suppliers.
Signs of GRP are the following; white looking edges, blackpaint and a fine weave on the underside.
Most proffessional mfrs will have batch and ID numbers incorporated in the product.
When paying several hundred pound its always better to have a good look before buying