Powertrix just needs better bearings for their upper a-arms, that's all. Otherwise you can get the same thing on ebay for much less. Guap's a-arms have failed bearings after a year of DD usage due to the same unsealed bearings that powertrix uses. Sealed bearings > Sheilded bearings. They don't cost that much more, so why not use them and have a more durable a-arm?