FAB Defense Glock 42 4-Round Magazine Extension Black. The FAB Defense Glock 42 4-Round Magazine Extension works by replacing the floor plate in your standard Glock 42 magazine to add 4 extra rounds of capacity bringing the total to 10 rounds in a magazine. If you plan to daily carry your Glock 42 pick up the FAB Defense Glock 42 4-Round Magazine Extension today. Specifications for FAB Defense Glock 42 4-Round Magazine Extension: Manufacturer: FAB Defense Color: Black Magazine Capacity: 4 Round Gun Make: Glock Gun Model: Glock 42 Features of FAB Defense Glock 42 4-Round Magazine Extension: Glock 42 only Enables a full grip on the handgun Contoured finger indents for a firm grip during magazine manipulation Innovative spring plate allows the use of the original magazine spring Fiberglass reinforced polymer construction Weighs 37 grams Package Contents: FAB Defense Glock 42 4-Round Magazine Extension What firearm models does the manufacturer say FAB Defense Glock 42 4-Round Magazine Extension is compatible with? The manufacturer suggests that FAB Defense Glock 42 4-Round Magazine Extension is compatible with Glock 42FAB Defense FX-4210B: Glock 42 4-Round Magazine Extension Black