Layer Cakes what is it? Collections consisting of 42,10" x 10" squares of 100% cotton fabric produced by many brands. (although that 42 number may vary). These fabrics are grouped together by designer line, color or theme. They are useful in making quilts since it enables the sewer/crafter to have a wider variety of fabrics in the pack and other 10" square precuts stem from the fact they are affordable, easy to use, and a size commonly used in quilting.