This ruler ruler features an extra 1/2" width for seam allowances; it is used to cut, square and trim blocks sized 12.5" and under when quilting. Omnigrid square rulers are used for secondary cutting of strips, and to square up finished quilt blocks. You can use with a rotary cutter or a straight-edge blade. It features a diagonal angle line and edge markings for accurate measuring. The laser cut edges allow for smooth, deep cutting. It has patented double-sight lines that show up on light and dark fabrics. It is made of heavy-duty durable acrylic material and had a left- and right-hand numbering and angle system.Details:12.5" x 12.5"Laser cut edgesDouble-sight linesAcrylic