P 51 Military Style Survival Kit Can Opener by US Shelby Co Pack of 4The P-51 is the larger version of the P-38 and was often used by mess hall cooks to open the big trays and large cans of chow. The P-51 is a full 2in long. The added length affords more leverage and doesn't require as much thumb pressure to use. Some prefer them over the P-38s bec..