Lets you scale metric with the familiarity of inches, and centering is easier.  Scale inches to inches, without a calculator, because regular inches are divided into units of ten instead of eighths.  Inches are paired with picas, on the same rule, and added a point/pica scale down the center of rule A.  On rule B, agates have been moved to the center in order to let the new decimal-inch be on the edge.  Points/picas remain on the other edge.  Inches and picas now appear on both rules which reduces the annoyance of  "picking up the wrong ruler."  Constructed of a lightweight but dimensionally stable polyester base, that is flexible, to permit measurements around the circumference of a cylinder.