They have interlocking sliding links in each one. The original idea is you bought a bracelet and a link to start then collected different links over time to replace the blank ones. Once your bracelet was full you would give the empty links and a charm to a friend who would in turn make a bracelet with their links. Very popular about tens years ago, they called them Italian friendship bracelets. Many places carry the links including the pagodas in the mall. Will try and take a picture and post later.