not all std bits fit the gsg. I wanted mine to look like a governmnet model, so changed;Fenix1 wrote: Assumed std bits would fit any of these.
the hammer (standard,but needed some sanding to get to fit)
the backstrap is fully interchangeable - but you may lose mag cutoff. I removed mine, but don't remember if it would fit or not.
the grip safety / beavertail is not compatable with standard! the bar that actuates it is a totally different shape. I still changed it, but it now does nothing and you have to cut parts off the new one to get it to fit, and you have to change it if you want a spur hammer.
mag release is not compatible with standard. it looks very close, but is different enough that I never put in the effort to do it.
trigger is standard