Veevus GSP White or Black
GSP Gel Spun Polyester is a super strong super thread, The world's strongest thread. $4.20 for 75 meter spools, (over 75 yards). Gel Spun is so much stronger than Nylon or other fibers.
Denier is the exact weight of the thread, 200 Denier is exactly twice as strong as 100 D
200 denier is over kill unless you are stacking deer hair for very big flies. 150 denier will do for most of the Musky Flies. Comes in Back or White.