I've been fishing furled leaders for 17 or 18 years now. All but two are made out of tying thread. I didn't make them. Over the years I've swapped flies and materials for them. Most are 5 feet in length. Some are made specifically for trout, others for tossing bass bugs. I store them coiled in small clear plastic envelopes. Over the winter I add several drops of liquid floatant to the bags, so they're ready to go in the spring. If I'm fishing for trout I use a 7 foot fluorocarbon leader from 7X to 4X. For warm water 4 to 6 foot fluorocarbon leaders ranging from 8 lb to 25 lb test. I use the two fluorocarbon ones with my intermediate line in salt and fresh water with 6 to 8 foot fluorocarbon leader, 15 to 30 lb test.