Glock Polymer Rear sight (OEM) 6.1/-1 provides the lowest impact. Generally issued standard with M/17L. Part number 2 on the Glock Schematic.
I like this lower sight because i like to take a center hold. The stock sights will shoot a little high for me. To install it use a nylon punch with masking tape on the end of the punch. Put the slide in a vice and use some protection material for it. The sights tap in easy and there want be a scratch on them done this way.
These sights (2) arrived very quickly in perfect condition, and for a good price. Not yet installed.