Cutthroat thread Streamer leaders are created with much more material in the butt section to aid in turning over heavier flies. These leaders are to be used on sinking lines / heads. We have many fishing guides out west using this leader on their sinking line setups. These Leaders sink faster than any other leader currently on the market. Also, because they hug the rocks / bottom of the river, they get your fly into the face of the biggest fish around. Sold with Tippet Ring.