This is a Pachmayr Base Pad known as the Grip Ext, model 03882.
Pachmayr's new Grip Extenders will greatly increase your control and shooting comfort when added to popular compact and sub-compact handguns. The extensions perfectly match the shape and texture of the handgun" so they look like they are part of the pistol" rather than an add-on. Extenders are easy to install and are made of tough" high strength polymer that stands up to the roughest handling. In addition" the Extenders come in a pack of two for a price similar to others on the market that only contain one.
Features:
Black finish
Replaces magazine baseplate
Extends grip surface
2-Pack
Fits Glock 26/27/33/39
.40 cal +1 round 9mm + 2 rounds