Helicoil inserts are precision formed screw thread coils worked into a diamond shape and wound into a spiral coil which is installed into helicoil tapped holes. They provide permanent conventional 60 degree internal screw threads. Helicoil inserts are larger in diameter prior to installation, during installation the inserting tool applies torque to the tang reducing the diameter of the leading coil permitting it to enter the tapped thread. Helicoil inserts are measured in installed length.