Product DescriptionUpgrade your FN Five-seveN Gen1 magazine with the CMMG 57AFD1E 10-round magazine extension kit, designed for fast installation without permanently altering your factory magazine. Built to match the magazine's contour, this extension kit includes a corrosion-resistant chrome silicon spring that is salt water-resistant and engineered to help maintain reliable feeding and long-term performance.Product Highlights Compatible with FN Gen1 Five-seveN factory magazines for 5.7x28mm pistols Quick install-replaces the floorplate without permanent magazine modification Durable lightweight polymer extension body with black finish Corrosion-resistant chrome silicon spring is salt water-resistant and resists taking a set Designed to match the contour of the Five-seveN magazine for a clean, factory-like fitSpecs Brand Name: CMMG Manufacturer Part Number: 57AFD1E UPC: 852005002028 Product Type: Magazine extension kit Caliber Compatibility: 5.7x28mm Magazine Compatibility: FN Five-seveN Gen1 magazines Capacity: 10-round magazine extension Material: Polymer (extension) Finish/Color: Black Spring Material: Chrome silicon (salt water-resistant) Package Contents: Magazine extension and springDisclaimer: We strive to provide accurate and up-to-date product descriptions, specifications, and images; however, errors or omissions may occasionally occur. We are not responsible for any inaccuracies or discrepancies in the content provided. If you notice anything incorrect or unclear, please contact us so we can correct it. When in doubt, we recommend verifying details directly with the product's manufacturer.