Spirit River designed these colors primarily for one of the most basic and abundant trout foods. We have also added just a touch of pearl blue Lite Brite many feel adds life to patterns. But do not be fooled by the name as customers around the country are using these dubbings for more than just shrimp and scuds. Spirit River leads the way in UV technology. As with all UV2 dubbings, these have a mix of primary colors that have been enhanced with UV Florescence and UV Reflectence dyes. We then blend these in with other fibers to achieve the over all base color while still giving it all the multi color property's of UV2. Each dubbing will kick out a host of color spectrums. Check them out in direct sunlight. *It is best to always use a pearl or silver Mylar under base or even basic white thread which will bounce any light back out of the pattern at a different wave length. Enjoy catching more. Quality and innovation at affordable prices. Proudly made in America .PATENT PENDING.