Helicoil Thread Repair Insert Size 5/16-18x .469 (R1185-5)Length of the Helicoil inserts are 1-1/2 times the diameter of the bolt, which provides sufficient strength in most applications.Inch coarseContains 12 insertsDrill size 21/64Brand: Heli-Coil, Model: R11855, Size: 5/16-18