JP's Nymphing Mud - Mojo Mud. Soft moldable tungsten putty that is just the best to use. Simply pinch a piece the size you want and mold it around your leader in a ball and then roll it between your hands to thin and spread it. If you need a little more, add a little and repeat. Need a little less, pinch some off and repeat. When you are done, remove it and add back to the supply. Since it's reusable, a little lasts forever. Comes in brown and gray colors.