Specifically designed for 386EVO cranks used in 68mm wide PF30 BB shells, this bottom bracket extends beyond the BB shell on each side to optimally position the bearings on the longer 386EVO crank spindle. This "XD-15 PRO' bottom bracket is equiped with Silicon Nitride ball bearings, which are 7 times harder than steel. These made in USA Grade 3 Si3N4 balls are the best ball bearings available. The XD-15 nitrogen steel alloy used in these bearings has proven it's superior corrosion resistance and longevity in aerospace applications. It's tough, long lasting, and the THE MOST corrosion resistant race material available. ALL OTHER ceramic hybrid bearings are a trade off. The ENDURO XD-15 Pro bearings deliver on all three key bearing requirements for "pro" environments: 1) Speed 2) Longevity 3) Corrosion-proof in any riding condition.