String-On Clasp has a Silicone grommet inside to securely hold the cording that you can thread through it. This replaces the need to make a macrame knot on all your bracelet or necklace designs. Also works for very fine, smooth chain. Also called slider beads or rubber filled beads or smart beads.
4mm x 5mm Hole size is approx. .7mm. By the each.