100% beeswax with ultraviolet absorbent dye. For all synthetic and natural bowstrings. Lasts longer than synthetic waxes.  Today's box strings are treated with ultraviolet brightener dyes when they are made. They glow and animals can easily see the string move on the draw. U-V-Block Bowstring Wax eliminates the ultraviolet glow of the bowstring, keeping you hidden from animals when bow hunting.