Can't remember exactly,
but it was kyosho America that told me about them,

A while back I owned a new kyosho Gigacrusher and it kept striping the 3speed spurgears,

And the extended pilot shaft broke on me,

I contacted kyosho America as I purchased the truck while on vacation in Florida,

And asked if there was an all metal upgrade bearing, they sent out the replacement parts and gave me the part number for the Duratrax bearing that fits the clutch on the Gigacrusher/Madforce,

It's been a while but I'm pretty sure these are the bearings,
http://www.ebay.com/itm/NEW-Duratrax...item43b1eae4be