The 3 Pack Premium Compatible 80%, Modulus, 1/4" ZrN Coated Solid Carbide End Mills by American Gunsmith Tooling are specifically designed for 80% Lower Receiver Jig Tooling. These end mills feature a single end design with 3 flutes, a ZrN coating for enhanced durability, and are made of solid American-made carbide. With a 1/4" diameter and a length of cut of 3/4", these end mills offer precision and reliability for your CNC machining needs. Made in the United States, these premium end mills are a valuable addition to any metalworking business or industrial application.