The plug is designed to close the open cavity at the bottom of the grip, not allowing debri to enter and reach trigger assembly and firing pin. It also fits flush to eliminate snagging on open cavity. Used by LE & military worldwide.
Very happy with the plug it came very fast and fit perfectly fine, fired 250 rounds through the Glock and it's installed very tight fitting . Will be buying more from this company
That only plug I found for the "sf" model that has the tab that snaps into the lanyard hole. It fits well but it is not flush