Hooked a large, but unseen, bonefish on 12 foot, 20lb test SA Absolute Fluorocarbon leader for saltwater and it parted 4 feet from its loop attachment to my grand slam fly line so no knot was involved. No barracuda was observed by the elevated guide. Must have been a manufacturing defect. Tied on a new and similar leader and hooked and landed an 8 pound bonefish. So, a happy ending after disappointment.