Hi Moaz, this will fit the Gen 5. The hole you see is for a set screw that holds the sight in place. You probably won't need to use it on the Glock, but it's there if you need it.
Stay safe & have a great day!

yes it will fit and work. The screw is for guns that have a loose fit of the dovetail

The set screw is for tensioning the sight to hold it in place in a loose dovetail. It might not be needed at all if it is a tight press-fit when installing the sight, but there are lots of aftermarket slides and such that one might find themselves installing these into, all with potentially varying machining tolerances.

Hi Moaz and welcome. Yes, these will fit the Gen 5 G19 no issue. The G19 is a dovetail rear sight so the additional screw would not be used. Cheers and stay safe!