Have you ever made a hooked rug only to find that your design doesn't show up well? This can happen because you don't have enough contrast between your colors. These clear plastic red and green filters work like magic to help you check out your yarns before you begin punching to make sure you have enough contrast. The red filter is used with warm colors and the green one is for cool colors. Look at your project through both and you'll be amazed at the results! Used at The Oxford Rug Hooking School to help students choose their yarn colors. Also great for quilters.