Centering Guide / Ruler (Fractions) Specialized ruler for use with Circle Guides and Degree Scales made by Circle Perfect Tools 0-13" ruler with increments marked every 1/8" (left side) and 1/4" (right side) Helps to draw lines and take measurements from a center pin hole A "Centering Guide" for the Router Table Circle Guide made by Circle Perfect Tools ** This product is included with the purchase of the Router Table Circle Guide