Product Description The NES 21 is a universal internal thread repair tool. This easy-to-use tool operates by adjusting the knob that sets the proper internal diameter of the tool to the good thread below the damaged thread and the 60 degree blade floats to the correct pitch. The NES 21 has a working capacity from 5/16 in. to 7/16 in. NES External and Internal thread restorers are the ideal tools for saving money during maintenance, plumbing, construction, agriculture, car repair and many other applications where there are components with a damaged thread. Compare the cost of disassembling the part in order to repair a component with the INSTANT repair that need to be performed with the NES External and NES Interal thread restorers. From the Manufacturer NES - The Thread Repair Experts - Nes thread repair tools are a complete line of tools specially designed to repair any defective thread, both internal and external. Our patented tools are universal in diameter and Pitch to give the user a comfortable, easy to use, fast and cost effective solution for any case of defective thread —in this we’re the experts! UNIVERSAL THREAD REPAIR TOOL - one hand tool repairs inch or metric, right or left handed, coarse or fine threads QUICK SIZING - no need for a caliper or pitch gauge to determine diameter or thread count or type RAPID ADJUSTMENT - tool adjusts and quickly adapts to particular diameter and pitch of fastener thread HOW TO USE - automatically chases good threads and the cutter repairs damaged threads QUALITY CUTTER - blades are made of High Speed Steel induction hardened to 62 Rockwell for longevity of life