Thick Black Rubber 3mm Tube Cord Necklace with Easy Locking Clasp - 18 inches. This 3mm thick black silicone rubber necklace features an innovative easy-to-use locking mechanism. Just squeeze the wide end and push the ball-tip into it. The result is a secure closure with a seamless look. String beads or chunky pendants onto the tubing to complete your necklace. Great for men or women. Necklace is 18" long, comes in gift box.