I bought night sights for my two CS9s online from Optics Planet. Had some problems with them repeatedly sending the wrong sight sets, but they finally sent the right ones (and yes, the CS45s are different---I had previously installed a set of those. Optics sent me those with no problems and they went on perfectly, shooting to point of aim). After I installed the CS9s, however, I had to call Trijicon to explain a problem I was having with them (my CS9s with the new Trijicons) shooting way low. They asked me to send in the slides. They managed to replace the front sights with some that have the dot resting right above the slide and even though I didn't buy 'em from them, they did it no-charge. My CS pistols now all shoot spot-on.

I also had a 3913 and a 3913 LS, both used, and both had severe accuracy
problems: one shot over 4" low, both had barrels that weren't milled
right and one (a "Lady Smith" variant) wouldn't group at all and was
shooting 7 & a half inches low. I sent SAW the slide of the 3913 Lady
Smith. They re-barreled it (at no charge) and it then formed a group,
but still shot 7 & a half inches low. For sights, S&W service department
suggested that I try a sight manufacturer, as they reportedly had no other sights available. I re-crowned the other barrel with the help of a machinist friend.

Sent both slides to Trijicon, who solved the remaining problems. They
installed a used, but perfectly serviceable, rear sight that was a
little higher on my LS, as well as a much lower front sight. This gun now shoots
perfectly to point of aim and sports night sights where before it had
just the standard Novaks.

As for the one that was shooting 4 inches low, this gun had Trijicon night sights on it already, so they installed a new, lower front sight, while harvesting the perfectly good tritium lamp from the old one which they used on the Lady Smith front sight. This gun is
not quite as precise as the Lady Smith---it now shoots two inches
high, but at least hits all "in the black" --- a big improvement.

And Trijicon did all of this (including return shipping) FOR FREE.

Anything else I ever decide to do with night sights I intend to send to them directly.