Shilen Thread Protector Blanks are designed to provide the gunsmith or barrel installer with a quick, precision solution, while also providing excess material required for the needs of the one-off custom build. Built on the “blank†concept each protector has precision threads and one square face with a thread relief of .08â€. The outside diameter is oversized, and the remaining face is left for final machining or blended by installer. Each protector is made one at a time from actual Shilen barrel steel and single-point threaded in house using precision CNC machinery. Â