Spirit River UV2 Peacock Herl - Spirit River has figured out how to make the darker colors fluoresce, which normally do not, by using their UV2 technology and double dyed process on the Peacock Herl which emits the UVR ultra violet wave lengths. Spirit River has figured out how to change the fly tying industry with the UV2 technology which adds a double layer of UV Florescence and UV Reflectance to their product line. UV2 TechnologyUV FlorescenceUV ReflectanceDouble dye process