I use Berkley FireLine Crystal for all my leaders. It typically sells for around $18 for 125 yards. The line has a thin diameter so the leader does not get overly "bulky". I have had thread leaders fail due to size of fish (king salmon and carp) and thread rot that ruined a weekend outing. I have furled mono, floro, uni, and polyester and I like the fireline the best. I have a feeling that there are not very many furlers out there that use fireline...... perhaps the expense is part of the reason. I spent $50 last week on more line and that's what got me thinking that giving away these leaders is starting to get expensive. Maybe I should furl some cheaper thread leaders and give those away instead.