Korda 4mm Rubber Beads

The beads are also great for use with a shocker rig, positioned between the lead and the backstop. They can also be used to protect knots and act as a buffer, as the tapered bore allows the knot to be located inside of the bead. They come in a choice of Muddy Brown or Weed Green, 4mm or 5mm, in packs containing 25 beads.

The small hole will then rest against the top of the anti-tangle system stopping the large bore of the back leads from sliding down the anti-tangle system which would stop the flying back lead 'flying' back on the cast.
Purely coincidentally, they are perfect for use on the Dark Matter leaders should you wish to fish them chod style and anchor the hook link on one of the two tungsten collars designed to hold the leader down on the lakebed.

They are also ideal for the shokka rig, which incorporates a running inline lead with a back stop set a few inches behind it on one of the leaders or on a length of rig tube.