Premium quality stainless steel threaded speargun adapters, made in the USA. At one end is 5/16"-24 male thread to fit into 5/16" threaded heads and at the other end is 7mm female thread for fitting to spear shafts with a 7mm threaded end. Fitting is 40mm in total length, but will add 25mm when threaded between your head and shaft.
Note: this adapter is made from quality 316 stainless steel - not tempered hardened stainless steel like many spears and heads. So please consider this when choosing to add an adapter in your set-up. This is not designed to be used as an extension segment for a spear, simply a means of adapting a thread size.