From Spirit River Flytying of the USA comes UV2 Dubbing.

Spirit River now has the ability to process fly tying materials with both UVF and UVR ... hence the name UV2!

UVF is the fluorescent wavelength in bright colours which allows fish to see flies at greater distance in most water conditions.

UVR is the reflective UV light that cannot be readily seen with the human eye, but is very visible in the animal and insect world. Bees use it to find flowers, mayflies use it to choose mates, and fish naturally key on it as a safe food choice. By closely mimicking Mother Nature's UV colour patterns, this new dubbing could give you a new advantage on the most wary trout.