For the tail of this pattern, I use marabou. When I push the fly down over the point of the hook, marabou passes through without any hesitation. I have used a variety of synthetic fibers and found that most of them tend to hang up slightly when passing over the point. Perhaps this does not matter with more powerful bites, but I am a fly-fisherman, so I want to increase my odds whenever I can. If I need longer fibers on top for greater length, I use a clump of marabou and tie the other material to either side so it does not pass through the hook point. Compressing or removing the barb is also helpful in getting materials to pass through freely.