Thanks guys.
Zeke, yes it's just the cheap plastic rear from Glock that I want to remove and install. Right now I have the 6.9mm rear, but it shoots too high at 25 yards. I want to switch to the next size down, the 6.5mm. It's the same cheap plastic and costs only $3.85.
So all I need is a wooden dowel and small hammer to swap them?