If you work with SAE, metric, National or British Pipe Thread grease Zerks, the Thread Tester will save you lots of time and frustration. When you're running multiple machines with a variety of grease fittings, or replacing a fitting for the first time, it becomes increasingly difficult to keep track of what's what. The thread tester provides a quick and easy way to tell all of your different grease fittings apart from one another.