The E-Zee Prime works with any popular brand of standard shell holder and allows instant changeover between primer sizes. It includes two primer trays, each of which incorporate their own built-in large or small primer punch assembly. There are no small parts to fuss with or lose. Each tray has a built-in shut-off gate to keep primers in place during change-over. The reloader simply removes the snap-in-place lock collar and installs the correct size primer tray and the shell holder as needed. Then, the lock collar is snapped in place and the change-over is complete. The primer trays also function as a primer flipper to properly orient primers for seating. The comfortable ergonomic design optimizes leverage to reduce hand fatigue.