Repair damaged 14mm spark plug threads by opening hole with a reamer/tap and screwing insert onto the spark plug. Use spark plug socket to install spark plug and insert. Remove plug and check that insert is properly seated. 

Set includes:
1 each of 4 inserts: 3/8, 7/16, 1/2 and 3/4" reach and thread locking compound.

Tap is designed for aluminum heads only.