These were for sale at the 2008 World Yo-Yo Contest and we brought some back for you too. These are the Gorylla Protoypes, the 511 has an Oxy 4 bearing, the 513 has a D bearing, and the 616 has an oversized bearing that we've not seen. These were made to see which would be more popular with the players. So tell HSpin what you think if you pick one up. There will be a no refund policy on these and remember they are used prototypes with marks and no packaging.