CURVE IT Echo® CURVED RULERS are arcs based on circles that stitch out the model numbers diameter. So if you use this CURVE IT ECHO® 12, you will stitch an arc, that if continued on, would create an 12-inch circle. Both sides of the ruler produce the same curve so you can use either side. The ¼” echo lines are based on circle arcs ½” smaller or larger (depending on which side you are using) than the circle arc you are stitching. Use the vertical numbered lines along with curve echo markings to create curved crosshatching. Also included are 45-degree lines and horizontal line. 1/4″ green acrylic. 8”x 4.75″. It’s 3” wide at numbered center 0-line. 'Curve It Echo 12', by Michael Davison of Quarter Squared Quilt Co.