The Graduated Square Frame Set contains six (6) coded durable plastic Frames in varying thicknesses. Now you can roll your Clay to varying thicknesses without the hassle of stacks of playing cards. Unlike playing cards or mat board, these plastic slats will not expand if they get wet, nor will they warp or wear out over time. They remain perfectly flat and the exact same thickness through years of use. Each frame is color coded by thickness, making it easy to find the size you are looking for.