Pack of 20 silver-plated wire protectors, approx. 4mm x 5mm. Use with beading wire up to 0.6mm (0.024”) in diameter. These keep beading wire from wearing against the clasp. Just thread the wire through a crimp tube, then through the protector, string your clasp so that it sits in the U-shaped portion of the protector, then go back through the crimp tube, and crimp as usual.