Our 5" circle (ruler foot seam allowance makes a 5" circle) has measured lines every 1/4" on the half side as well as diagonal markings on the 45˚ angle and is perfect for Circle Quilting and scallops, half circles and heavy arcs. The ruler measures 4.5" in diameter and is made of 1/4" acrylic which is safe for use with machine quilting ruler work with a ruler foot and will work with low shank machines.