I saw this at a gun show and thought it the handiest tool. Not only is it a sturdy armorer's tool but it can attach in that hollow behind your magazine well so you will always know where it is! Here is the info from the package:
Snap-in tool provides pin punch and ejector remover. Protects inside of Glock from dirt & debris. Allows detail striping in field. Precision-machined Delrin with steel pins. Blends nicely into Glock Frame. Weighs less than 1/4 oz.
I installed this plug into a Glock 19 and it does indeed blend in. One thing omitted from the write up is that this plug stays in place with a neat little delrin spring-loaded pin. Looks very sturdy and I seriously doubt it could pop out on its own. It's a pretty neat tool and one worth picking up.