Senyo's Fusion Dubbing is a great dubbing material for larger patterns such as traditional streamers, large nymphs and especially for leech patterns given the long fibers.  This product is a blend of Trilobal and Ice Dub in 14 fish catching shades that even the most discriminating fly tyer will appreciate.

In a pinch this also can be used for finer tapered flies but remember to use a light wax so that the fibers will roll onto the thread and stay there while you tie.  As always, tight lines