these are custom made adaptors from a solid piece of aviation stainless steal. its a direct bolt-on that are square shaped that will fit most fg gpr tire plus more ,as long as they have the same hub they will fit. they will be available for purchase soon
http://i1048.photobucket.com/albums/s366/Rogerrodriguez87/REVO.jpg
http://i1048.photobucket.com/albums/s366/Rogerrodriguez87/EREVO.jpg
This is a E-REVO with fg tires. Its a great setup for top speed runs, its also very stable due to the tire not ballooning or running the risk of a high speed tire blow out, which you would normally get with foam insert tires. You can even put bigger tires that would only fit 1/5 truck/cars for off road usage