These add weight & make a pretty impressive hotspot. Flat 2.8mm brass collars which slot into a countersunk brass bead. Flybox or Veniards beads would be perfect to use with them.
These collars fit onto both 2.8 or 3.2mm beads but probably work best on 3.2mm. Looks better with the collar slightly smaller than the bead, like you would tie a floss throat...which is essentially what they mimic, but much better!