This 5/16inch (8mm) diameter, kinkless, heat resistant stainless steel ball chain is ideal for using on fire poi. So good, in fact, that we use it ourselves. If you're repairing or making your own fire poi then we'd recommend you use it too. With a tensile strength of 120lb (54kg) you'd have to use your poi as a rope swing (please don't) in order to break this ball chain.