Key colors infused with UVF and UVR. Read more about this or watch me talk you through it on You Tube. We buy this as 6-7 inch strung saddles.....which means its usually runs 5 to 6.5 inches. Ours is some of the best in the industry and we have a extensive line of regular or ultraviolet UV enhanced saddles. These are strung and being from a rooster they have a stiffness and bounce. Spirit River continues to lead the way in UV2 technology. We have used a double dye process to give all our unique UV2 materials and flies the added UVF/UVR ultraviolet wavelengths. We all know UV Fluorescence which is so common on everything from street signs to bass lures. UV Reflectance is a spectrum of wavelengths humans can not perceive yet is extremely common in the animal and insect world. UVR allows mayflies to find mates, and bees to find flowers. Many male birds and bugs have a strong natural UVR signature. Check out my You-Tube tying videos with our UV2 products and thanks for supporting us and our dealers. Here is a easy link. http://youtu.be/wXmC7aN8F-A Another link shows me tying a Wooly Bugger which uses a saddle palmered across the body. http://youtu.be/1cGB9f1oYlc Remember.....we are a small Oregon family based business and we appreciate your support as do our dealers nationwide. Always visit your local fly shop. They work hard and deserve your business.