Just one knot and it's one of the strongest about. The Mahin knot. I lost a fish on the undercut island Friday night. Fish shed the hook and I was left stuck to likely a root. The knot st the hook link swivel gave before the leader knot.
For the invisibility factor it's well worth it. If I could get the leader in 15lb I'd use it at that BS but 20 is the lowest.