M16 x 1.5 mm Metric Thread Repair Kit by Cal-Van Tools?«. In the above models a common problem is the spark plug tends to break off in the cylinder head during maintenance. If this problem is not repaired properly, it can result in damaged or unusable spark plug threads and in extreme cases the possibility of a spark plug blow out. This kit will allow the user, with simple step by step instructions, to repair those damaged threads or blowouts in 30 minutes or less per cylinder.