We have found dupes tru out the KK series of discs .It is not needed to buy 301 and 302 if you buy the dec 2009 set (400 series) for the $$ it is worth it to buy the 300 and 400 series. We have found ebay to be our best outlet. We have not purchased any before the 300's so I cant help here and have not found a online or brick and mortar store that carries them all. I hope this helps