Product DescriptionThe B5 Systems Sierra K Receiver Extension Kit is the proprietary mounting system designed for the Sierra K Buttstock. Built from mil-spec materials and finishes, this reduced-length kit is engineered for compact builds while maintaining durability and reliable function. It includes a 5-position receiver extension made from 7075 aluminum, along with the key buffer system and mounting components needed for installation. Proudly made in the USA.Product HighlightsProprietary Sierra K mounting solution featuring a reduced-length, mil-spec diameter receiver extension7075 aluminum, 5-position receiver extension for strength and adjustable fitIncludes short heavy buffer (3.5 oz) and extra power spring for dependable cyclingComes complete with castle nut and quick-disconnect (QD) end plate for secure mounting and sling compatibilityMil-spec materials and finishes; Made in the USASpecsBrand: B5 SystemsProduct Type: Receiver Extension Kit (Sierra K)Manufacturer Part Number: SRK-1660UPC: 814927024793Color: BlackReceiver Extension: Reduced-length, mil-spec diameter, 5-positionReceiver Extension Material: 7075 AluminumIncluded Components: Receiver extension, short heavy buffer, extra power spring, castle nut, QD end plateBuffer Weight: 3.5 ozCountry of Manufacture: Made in the USADisclaimer: 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.