I bought this for my Sig M18 (ProForce airsoft). It looks amazing on it and provides a comfortable grip (not that the original grip is not good) and a different look.
It only requires the replacement of the selector pin (for which you need a really thin allan key) with the provided pin - which is fairly easy to do.
However, only the long-type magazine would work best with this frame. The short-type magazine needs to have the side "flaps"trimmed" to fit in properly.
The magazine also won't fall freely afterwards and the button plate will not properly match the contour of the mag-well.
My advice would be to buy additional bottom plates for the short mags and modify those.
Using this frame is also a good way to turn your M17-M18 pistol into a dual-tone piece :)