Nautilus GTX Reel BlackNautilus GTX Reel, The GTX is a 5 inch diameter fly fishing reel with a 1. 1 inch wide spool that can hold up to 500 yards of 60 lb braid. That's a lot in a narrow frame. You will also be amazed at how light the spool is, especially in a reel that is designed to turn a fish that is as big as you are. As youve come to expect from a Nautilus, the reel is intricately machined with their Giga Spool Design to ensure strength, optimal line pickup, and