A couple weeks back I received some prescription oakley's I ordered from the local optometrist office. They are called crosslink float EX. They come with clear and shaded lenses. It looks similar to the crosslink switch and the lenses swap out through a movable nose piece and latch system. I looked these up online to see about future replacement parts and this model is nowhere to be found. Is it possible I bought expensive knock offs, or does oakley only have certain prescription glasses available through dealers?