The Cressi Quick Bridle Beads are sold as a pair and are what is used to make up a bridle to insert into the speargun rubber. Without bridle beads, it would be very difficult to load a gun as the beads are what stop the bridle from coming out of the rubber when loaded.
They are pushed into the gun rubber, using some silicone spray and a T-tool, and then tied off with constrictor cord. Beads can be reused but due to then being so cost-effective, you would normally just purchase some more
