I questioned that when I contacted TruGlo, and of course there is no practical way to lower the front sight or raise the rear sight. I primarily concentrate on my front sight when shooting combat and may align the 3 dots. Aiming for center mass at combat distance, differences will be insignificant but if your shooting at 25 yards or more at bulls eye or target there will be a lot of difference.

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640Pro 340PD Shield M&P 22