I used to use Pro Grip all the time shooting Glocks and si gle stacks. Last match it was really humid so my buddy and I were both using it with our STI's. His mags quit dropping free a few times and I started getting tons of failures to feed. Cleaned gun and ran same ammo in same conditions without pro grip all over our hands. Problem solved. Needless to say I won't be using it when shooting 2011's anymore.