I am giving this a 4 stars because this is only my initial impression. I am waiting for my long term experience before giving the last star. My initial impression is positive. I ordered one plus one and another plus two spring set for my M&P Shield. Changing out the internals was rather simple and straight forward if you have any experience or you are mechanically inclined. At first I was a bit concerned because the magazines loaded almost too easily. I was able to load 5 or 6 rounds simply with my fingers. In my experience new magazines have been more difficult to load until they have broken in. I wondered if they would have the force necessary to feed all rounds and lock the slide back after the last round. I loaded both magazines and took them to the range with 200 rounds for my first test. I must say I was pleasantly surprised. I fired all 100 rounds alternating between magazines with out a single malfunction. No failures to feed and no failures to lock the slide back on the last round. I have begun a long term test to see how the magazines, specifically the springs handle the pressure of being compressed over time. Since I bought them in July I will check them again in December around Christmas. If they pass that test I will check them again around July 4th next summer. Some test simply take time. I will check them with another 200 rounds then and if they perform as expected I will give them the final star.
