Are you thinking about installing an extended mag button? IF you are, consider getting a G20/21 button for just a coupla bucks instead of spending around $15 for a "real" extended mag release.
A G20/21 button will pop right in and, IMO, extends it out to just the right length.
It's the same button they put in the G34/35 series.
I believe that's what this is. Stephen Cue is wanting to trade his extended Glock release for a standard one. His is installed in a G22, and my standard is in a G19.