Stainless Steel Spacer Beads, 4mm (.16") with 2.1mm (.08") Hole, Pack of 10
Hollow bead is 4mm (.16") round.
Hole size is 2.1mm (.08"). In order to slide this bead on, the end of your chain will need to fit into a 2.1mm hole. Sometimes you can remove a clasp (if it's attached with a jump ring), slide the bead on and then add the clasp back on.