Gel spun Polyethylene thread by Veevus. Strongest style of thread available, great for tying streamers and other patterns that require a lot of thread tension.
PRO TIP: when tying streamers the thread is usually only visible near the eye of the hook, where the pattern is finished/tyed off. We use white GSP to tie with, and then use a marker to color the finishing area, and finally top it off with Tyer's Z-ment, or Loon UV Flow.