The steel gauge is designed to fit into your slide, enabling precise measurement of the hood length to an accuracy of one-thousandth of an inch. It provides the exact amount to cut initially, thereby eliminating the time-consuming process of filing, fitting and repeated adjustments. The EGW Hood Length Gauge is an optimal instrument for efficiently measuring the precise dimensions of any barrel's hood length Heat-treated to a hardness of 55 Rockwell C (RC) for extended durability