This is a tricky fly to tie and it takes a fair amount of practice to get used to working with Antron to get the “bubble” formed correctly. Tightlines production has a nice video that I found very helpful. For the tail I pick out a few fibers from the Antron sheath with a bodkin and twist them together. This is best done before you trim off the excess Antron after securing the sheath. One trick I've found is that the bubble gets twisted a bit when you make the first wrap at the head of the fly to secure it. You can "detwist" at this point to unwind it a bit (you can see in the picture below there still is a slight twist in the antron sheath) and then secure it with some tight wraps of thread.
TMC 100 #16 or #18
underbody – tan dubbing (I use antron)
Antron bubble – tan antron fibers
tail – a few antron fibers picked out from the bubble
comparadun deer hair wing
thorax – brown squirrel SLF dubbing