Brake Master Cylinder Rebuild Kit. The All Balls Brake Master Cylinder Re-build Kit contains all of the components required to re-furbish one master cylinder. Sold as a complete kit by position. Note: Kit contents will vary by fitment and are subject to change. Kit includes: 2 cup seal(s), master cylinder. 3 washer(s). 1 boot. 1 spring(s). 2 screw(s). 1 snap ring(s).