5/16" BSW x 18TPI - Wire Thread Inserts are produced from profiled austenitic stainless steel wire wound into a helical spiral, V-Coil free running inserts have a spring like appearance. When installed, using any one of a variety of manual or automatic tools, they provide strong permanent internal threads which resist head and corrosion. Once fitted, their position is maintained by the action of radial pressure between their coils and the flanks of the tapped hole. This pressure exists because their free diameter is larger, by a calculated amount, than their installed diameter. 

We also stock full thread repair kits which will include wire inserts and tooling, these are available here - https://www.gwr-fasteners.co.uk/thread-repair-kits-3177-c.asp

As well as the thread repair kits, the tooling is available separately here:

Extracting tools - https://www.gwr-fasteners.co.uk/extracting-tools-3204-c.asp
Insert Tools - https://www.gwr-fasteners.co.uk/insert-tools-3194-c.asp
Tang Break Tools - https://www.gwr-fasteners.co.uk/tang-break-tools-3203-c.asp

This is not a stock item therefore please allow 1-3 working days for dispatch. As this is not kept as a stock item, this is non-returnable & non-refundable.