This unique ruler is perfect for squaring up or centering traditional quilt blocks, applique blocks and machine embroidered blocks and features the unique Non-Slip Coating. The inner area of the ruler has a 5.5 x5.5 in opening with measurement markings from center out. The outer edge measures 7.5x7.5 in with traditional left to right measurement markings. All measurements in 1/4 in increments.