ST-66 are wicked strong. I lost a big bluefin, looked about 100# minimum just outside of gaff range on my last trip just before Thanksgiving. It freaked out at the boat looming overhead and surged away, ripping free. It had fought for fifty minutes with a single barb of the 5/0 ST-66 bottom hook on my knife jig snagged on his side above and behind the left pectoral fin. I regret that I was too tired to think of taking a picture of the piece of skin on the barb. But I can't think of another treble hook that could have taken that punishment.