Well, between our 4 tsunamis we have now, we have broken at least 3 or 4 of the rear drive shafts! They sheer right off on one end or the other right at the ball. I found that the "local" (30 min drive) Hobbietown USA carries a HPI 6x57mm dogbone part number A553 and they fit right in perfect. These hpi shafts look much heavier duty at the ball, and also feel like they weigh considerably more. They also cost $1.50 more a pair than the redcat ones from Clermont, but after comparison I think they will be worth the money.