Square Ruler Value PackThe Omnigrid 12 1 2" square value pack contains one each of 4 square Omnigrid quilting rulers (4 1 2", 6 1 2", 9 1 2" and 12 1 2"); each has an extra 1 2" for seam allowances and diagonal angle lines; use them to cut, square and trim blocks. Use with a rotary cutter or straight edge balde for secondary cutting of strips and to square up finished quilt blocks Diagonal angle line and edge markings for accurate measuring Heavy duty durable acrylic