Pearce Grip Grip Frame Insert, For Glock Gen 4 29 and 30, Black Finish PG-F130G This unit installs in the bottom rear cavity of the frame utilizing the lanyard hole for retention. Made of a high impact polymer" this insert is designed to keep out dust and debris as well as finish off the overall look of the frame. Its design also allows for use with or without the factory interchangeable backstraps.