T o be picky, the only "new" thing is putting all the pieces in one kit and selling for $55, which is about a $5 reduction.
On the plus side, it is about as good as you can do if you want to improve the SD action above S&W stock parts.
Add in the cost of night sights and it gets close to the cost of an M&P Pro that comes with the goodies installed from OEM.

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Science plus Art