Avid Titanium Pivot Balls for the Xray X4 are 6mm in diameter with M3 threads and a lightweight option for the kit steel part XRA303260. What makes these low traction balls is that the threaded shaft is 6.5mm instead of 5.5mm so you can run more shims in order to raise the roll center. Like all of our titanium parts made here at Avid RC, they are of the highest grade billet 6Al-4V Titanium to ensure the best strength possible.