These are a silly gimmick which only work when the target is at a single, specific angle relative to the mag baseplate. The 20 round mags do not share the same baseplate angle in most brands, so the required relative height of the target vs. shooter would change. The stability would not change, and as mentioned in the other thread, these only influence stability in the smallest way. Not worth the cost. Btdt, not silly enough to go back.