HHIP 31 Piece 5/16-18 Helical STI thread repair kit for repairing tapped holes. Simple and easy to use kit. Cost effective system creates stronger than original threads. Kit includes 25 Stainless Steel 5/16-18 Inserts, 1 5/16-18 STI High Speed Steel Tap, 1 piece of a 21/64" High Speed Steel Twist Drill, 1 Coil Driver, 1 Tang Breaker, 1 L Hex Wrench, and 1 Metal Case. Installed length of the stainless steel inserts is 1. 5 X diameter.