[usouthnurse]

Is there a gen 4 21sf? If so, do the gen 3 mags also fit in the gen 4 sf and vise versa?

 

[Gravity3694]

Yes, there is a gen 4 G21. Since the backstraps are interchangeable, the size can be made identical to an SF. Gen 3 mags interchange as long as the mag release is set up on the left side for right handed shooters.

On a side note the gen 4 G20 just came out. The G21 gen 4 has been out for over a year or so IIRC.