Are you asking if a Glock can hold higher cap mags? If so yes. There is nothing in a Glock that prevents larger magazines (as long as they are Glock) from working in them.
A Glock 26 can use its standard mag (10 rounds) or it can hold a Glock 19 mag (15 rounds) or it can hold a Glock 17 mag (17 rounds). Of course the mag will stick out the bottom a lot. It can even hold the 30 or 33 round mag.
If your question was something different sorry I mis-understood it then.