Omnigrip 2-1/2-Inch-by-18-Inch Non-Slip Quilter's Ruler Omnigrip Non-Slip Quilter's Ruler features a right and left handed numbering and angle system Triangle cuts are easier with the diagonal lines Has an extra 1/2 inch on two sides for seam allowance This 2.5 by 18 inch ruler has 30, 45, and 60 degree angle markings