I got the Sprinco recoil reducer for my P99 (9 mm) a few months ago and I must admit that I was not impressed. Although it's a well finished piece, it proved to be too long for the slide of my 9 mm (which is a bit shorter than the .40 slide), so I had to shorten it about 4 mm. Also encountered problems due to the edge of the forward part of the guide rod bouncing against the circumference of the bore (passage hole for the recoil spring guide rod) in the slide and leaving marks. I also solved this by rounding the edge of the rod but by doing so, the weight decreases and the dampening effect also decreases a little bit. After these modifications, it functioned satisfactory. I keep it for shooting 'hot' loads while I shoot moderate loads with the factory spring.