Well you get what you pay for! I haven't tested this, but wouldn't expect much for $200. Actually I think you can get it for $169 from Amazon.com!
The aperture is very slow: f8.3-f11, which becomes f16-f21 with the 2x converter.
This will produce a VERY dark view through the viewfinder and is probably too slow for most cameras to reliably autofocus.
But if you've only got $200 to spend, then it's an option - just don't expect miracles! There's some interesting user comments on Amazon's pages.
The official page is here:
http://www.opteka.com/index.asp?PageAct ... D&ProdID=8