The Good Measure 22-1/2 Degree Wedge Ruler is used to make tumbler blocks, dresden plate blocks, and grandmother's fan blocks. The 22-1/2 Degree Wedge Ruler requires 16 pieces of fabric to complete a circle. Good Measure rulers can be used in combination to create unique quilts. The 22-1/2 Degree Wedge Ruler is transparent and features easy-to-read gridlines for accurate marking and cutting. Good Measure donates a portion of each ruler sale to breast cancer research. Made in the USA!