Avid continues to use their proven Taperbore master cylinder design for 2012, but has made major changes to the internals.  The new version (<i>right</i>) has its bleed port on the main lever body, allowing it to forego the extra sealing O-ring that the previous version (<i>left</i>) requires between the contact adjustment dial and lever body. The side-by-side comparison also clearly shows the difference in how the inside of the master cylinder is shaped on the new version in an effort to better control any air that may be present in the system, preventing it from getting past the seals and into the brake line.