Shadow Systems CR Magazine Basepad Extension 3 Round. The CR920 was designed with an extra powerful magazine spring from the very beginning so you do not need a different magazine spring when converting a 10-round magazine to a 13-round magazine. Specifications for Shadow Systems CR Magazine Basepad +3 Extension: Manufacturer: Shadow Systems Magazine Capacity: 3 Round Gun Make: Shadow Systems Gun Model: Shadow Systems CR920 Features of Shadow Systems CR Magazine Basepad +3 Extension Complete drop-in assembly (front section rear sections locking pin) Fits CR920 Package Contents: Shadow Systems CR Magazine Basepad +3 Extension What firearm models does the manufacturer say Shadow Systems CR Magazine Basepad +3 Extension is compatible with? The manufacturer suggests that Shadow Systems CR Magazine Basepad +3 Extension is compatible with Shadow Systems CR920Shadow Systems SG9S-00-56-EXT: CR Magazine Basepad Extension 3 Round