For adjusting the action of squid jigs in different conditions e.g. fast currents, deep water. Wrap around the front of the jig to make it sink nose first, or as in the second picture around the body and eyes to get a more horizontal sinking style. Best to use glue also to secure it to the jig. The luminous tubing isn't bonded to the lead and can be slid off.

One 25 cm length weighs 1.9 g.
Lead diameter is 0.8 mm
Luminous tube diameter 1.5 mm