Made from implant-grade titanium, these beads are designed to snap into captive bead rings. Flat on the back, these have a single bezel-set gem on the front. Except for a limited selection of cabochons, all stones are synthetic. 2.5mm beads fit 16g and small-diameter 14g captive rings.3mm beads fit larger-diameter 16g and small-diameter 14g captive rings.4mm beads fit larger-diameter 14g and 12g captive rings. If you order a captive gem bead and captive bead ring together, we’ll make sure you get a bead and ring with a good fit.