A base pad adds the mass that helps the G48 magazine exit cleanly after the release, without depending on spring tension alone. The G48 is Glock's slim compact 9mm, and its slim-line magazine is not interchangeable with standard G19 double-stack magazines -- base pads for the G48 are specific to the slim format. For G48 shooters who train seriously or run the gun in single-stack style events, a base pad that drops consistently is the same worthwhile modification as on any Glock.
Confirm compatibility on the individual product page before ordering.