This will mill your standard frame size Glock (G17, G19, etc.) for the Aimpoint Acro red dot. The Acro is a closed emitter red dot which will clamp onto this milling, so there are no screws to fit. Your Glock should come back ready to drop your red dot straight on. It will remove your rear sight, so if you want to run cowitness iron sights, you will need to have a new dovetail cut ahead of the red dot. WE only cut it it this way to get the optic as low as possible, by leaving the rear iron sight the depth of cut is very shallow, and we don't think it worth it.