This is a synthetic type of yarn that is stretchy and has long continuous fibers. You won't find a better egg pattern yarn and it also works nicely for sculpted head or body patterns that might use wool.
SemperFli Nano Silk Ultra Fine 50D 12/0 - Ultra strong and ultra fine GSP. Ideal in situations where strength and minimal bulk are necessary. Very slick. Split-thread technique can be used with this thread. Ceramic bobbin recommended. 50 yd spool.
Ultra-Strong GSP (Gel Spun Polyethylene). Great if you have issues breaking thread due to too much tension or if you have bugs you really wanna crank on, like deer hair head bugs. It ties flat for low bulk. The higher denier you go, the stronger the thread will be.