Old farts like myself remember the days when bait-casting reels were often spooled with braided line (mono was still catching on for use with conventional reels). This line was nothing like the small-diameter, slippery braided lines of today. It was low-tech stuff, and I don't know if it's even made anymore. I certainly can't find it.
I find that that old-fashioned line makes the very best stopper knots for slip bobbers, and best by a huge margin too, but I'm running out of my ancient supply. I also find that the store-bought, pre-tied stopper knots are made using just about the worst choice of material, because after a several casts and passing through the rod guides, the line starts to fray and the leading edge of the knot puffs up and it can't be re-snugged on account of the fraying. Then, if it snags badly on a rod guide during a cast, and at some point it will, you'll get the worst backlash ever if you are using a conventional reel. Gosh, I'd like to find some more of that old-fashioned braided line, just for bobber-stop knots. Anyone have any ideas, or a next-best alternative?