The J-Plate directly replaces the factory baseplate on the Magpul GL9 PMAG for GlockA(R). The J-Plate is 6061 hardcoat anodized aluminum, and features laser marked identification numbers. The plate is easily installed, utilizing the factory retention plate. The plate also adds additional weight for fast magazine changes. Direct drop-in replacement of factory base plates Utilizes factory retention plate Adds approximately 0.045 ounces to the magazine weight Works with Magpul GL9 PMAGS-MAG546 and MAG550 only. Will not work with factory GlockA(R) magazines. Mfg: Apex Tactical Specialties Inc SPECS: Works with Magpul GL9 PMAGS-MAG546 and MAG550 only. Will not work with factory GlockA(R) magazines.