I installed these on my Glock 27 magazines. Overall, the flat bases were fine, but I was not completely happy drawing from a concealed carry position. I was looking at going with a Glock 23 or 19. I may do that later, but, for now, these extensions help me with my grip.Please note a couple things: These are not the ones to add round capacity to the magazine; they are just to help those who want help with grip. Also, you should have a Glock tool or something like it. The Glock bases come off easily if you do things right. It is not like those metal magazines you may have disassembled. You can look up videos on YouTube to see how it is done. The Glock tool needed to go in deeper and wedge the spring before I could remove the base. The magazines really do not squeeze in on the sides as the directions seemed to say. The Glock tool actually gave me the leverage to get the original base off.