Heli-Coil 5521-5 5/16-18 wire insert repair kit
Check compatibility
Heli-Coil 5521-5 uses a wire insert for 5/16-18. Match the 18-TPI pitch rather than selecting by the shared 5/16-inch diameter.
Questions before ordering
How do I tell if the 5/16-inch fastener is coarse?
Measure the pitch and confirm 18 TPI. The nominal 5/16-inch size alone also describes the separate 5/16-24 fine thread.