Mine just arrived this morning. I must say that i've seen similar quality frames for sale for hundreds of pounds.
(following posted as review on amazon.co.uk)
It can be worn with the outer 'sunglass' lenses with or without the optical inserts behind it, or, without the outer 'sunglass' lenses with the optical inserts alone - you can get coloured lenses for your optical inserts so that it would serve as sunglasses itself without the outer sunglass lenses. That way, you can remove the outer curved lenses and just wear the frame with the optical inserts thus providing a quite unique design for which you might have to pay hundreds at your local spectacles store.
My only quibble with the design - hence 4 instead of 5 stars - is that instead of black-rimmed optical inserts, XLC would have done better with a 'screw-on' optical-insert design that allows one to get rimless prescription lenses, and fasten it into a cylindrical-shaped obtrusions at the bridge behind the outer 'sunglass' lenses. Wonder why it didn't occur to them. Hmmm...perhaps i ought to patent that idea;)
Anyway, i would certainly recommend this frame for those whom think, like I do, that the spectacle industry is industriously ripping off people with high-priced frames that probably only cost a couple of pounds to produce.