XM Series by QA1. These joints are simply the strongest and best available with superior load ratings and a self cleaning Kevlar/Teflon liner. Body is built from Chrome Moly alloy steel, heat treated and coated for protection. The race is self lubricating and self cleaning. The ball is 52100 hardened bearing steel, heat treated, hard chrome plated and precision ground. For top notch performance at a good price the XM series should be your choice.