A fine powder floatant with dessicant crystals that help remove moisture from your fly. Drop the fly in with leader attached, close lid gently so as not to crimp leader, shake bottle a few times, take fly out and tap off excess powder (keep the wind at your back), and cast the fly. (Seems to be more effective if you start with liquid floatant on non-CDC flies and switch to the powder when fish slime overwhelms the liquid floatant. The powder seems to cling to the residue from the liquid floatant).