The Terra Fly Tying Bobbin is a simple bobbin that J&B uses in the store to wrap jig heads and whip hollow core splices. Much simpler than some serving tools this bobbin is fast and effective. The Y shaped arms give spool tension the flared tip insures that thread will not chafe or groove the bobbin. Pro Tip: For more tension take one or two wraps on the Y arm with the tread before going through the serving tube. J&B uses power-pro wound on a thread spool for serving Top Shots, it is strong and abrasion resistant.