The Grace Company TrueCut Rulers have a track that works with the guide on the rotary cutter. As you move the cutter along the ruler"s track, the guide keeps the cutter from veering away from the ruler"s edge. Provides an easier, safer and more accurate method of cutting 6.5"x 12.5"- TMeasured in 1/8" increments, built-in spaces for marking your fabric directly through the ruler, and labeled .25" and .75" marks for easy measurements. They have built-in seam allowances on one side, and include 30, 40, and 60 degree angle lines