The Babylock is our most popular lock--used as a connector, a clasp, a charm holder and for many, the very first lock that they purchase. It measures 1.5CM X 9MM with a thickness of 3MM Closure is 4MM. The Babylock fits on all chains, or strands. Ideal for a necklace. They have six sides and can be engraved with up to 3 letters, numbers of symbols per side. Fun fact about the Babylock: 12 linked together make a bracelet for an average sized wrist. And yes this has been done more than once.