This thread is a stranded form of GSP which has incredible strength for its size. Advertised as "almost unbreakable", it allows tying techniques never before possible while minimizing thread build-up on small flies. It is loosely twisted so, unlike other GSP threads, can be split for dubbing loops if desired, although it is fine enough to be doubled for loops without excessive build-up. The white thread takes marker colors easily. This 50 denier thread has a breaking strength of 67 oz. (1.90 kg). 50 meters per spool.