##Enduro ABEC5 71806 Bottom Bracket Bearing 30x42x7 (Single) Stepping up the quality from ABEC 3 for this Enduro ABEC5 71806 Bottom Bracket Bearing 30x42x7 (Single) gives a welcome increase in performance. The materials used here are of superb quality, especially the military grade high precision HRC-64 hardened Grade 5 Chromium Steel Balls that are housed within the 52100 High-Carbon Chromium-Alloy mirror polished races. If this does not mean to much to you then do not worry, all you need to know is that this gives you bearings that can use double the tolerances of the ABEC 3 range. It also reduces noise from this high pressure area. Even the materials of the retainers, nylon and graphite, give near frictionless motion as well as constant lubrication to increase the life of your precious bearings.