Add our +10 extension kit to your Glock 31-round magazine and transform it into a giggle-worthy 41+1 round BIG stick.
This is the same extension as our well-known 170mm +8/10 but it ships with a crazy-long machine-pistol spring.
"NOTE: Because of a combination of factors, we build our basepads slightly "short" for best reliability. As a result, they will run properly with ammunition loaded to 1.125" overall or less. That's a typical length for 115- and 124-grain loads, but some (notably, Winchester 115 RN) will go out all the way to 1.160".