I just bought my first pair of Ray Bans -- New Wayfarer Sunglasses Camo Green -- and I'm very happy with them.  I had bought knock-off clones trying to save $, but have found that they don't stand the test of time.  It must be noted that $20 knock-offs are definitely not as well put together, and the lenses are inferior by far.  One of the lenses from my last pair of knock-offs came apart from the frame.  So my recommendation is that for $75, it's worth getting the real thing -- just don't lose them!