When high pressure clamp bolts are used frequently the threads will wear down eventually causing the bolt to fail. User's need to replace their high pressure bolts at the first sign of the threads wearing down or being marred. It is not recommended to tighten these bolts with an impact gun because it may cause the threads to be marred or jump threads causing the bolt to become stuck on the nut. These are replacement nuts for High Pressure clamps and are made of brass and have a 5/8" Hex with a 3/8"-16 Threading. After repeated usage nuts on high pressure clamps will wear down and you will notice filings on the bolt when you notice this it is time to replace the bolts because they may fail unexpectedly.