{"product_id":"ergo-4971b-castle-nut-ar-15-ar-10-steel-black","title":"Ergo 4971B Castle Nut AR-15\/AR-10 Steel Black","description":"\u003cp\u003e\u003cspan style=\"font-size: 14pt;\"\u003eThe \u003cstrong\u003e\u003cspan style=\"background-color: #ffff00;\"\u003eErgo 4971B Castle Nut\u003c\/span\u003e\u003c\/strong\u003e is a \u003cstrong\u003eMil-Spec CAR castle nut\u003c\/strong\u003e machined from \u003cstrong\u003esteel\u003c\/strong\u003e and finished in \u003cstrong\u003eblack\u003c\/strong\u003e to secure the receiver extension (buffer tube) to the lower receiver on AR-platform rifles and pistols. It is engineered as a direct-fit, durable replacement for the factory castle nut, delivering the same reliable buffer-retention function expected of mil-spec hardware.\u003c\/span\u003e\u003c\/p\u003e\u003cp\u003e\u003cspan style=\"font-size: 14pt;\"\u003eBuilt to fit \u003cstrong\u003eAR-15\u003c\/strong\u003e and \u003cstrong\u003eAR-10\u003c\/strong\u003e lowers as well as \u003cstrong\u003eall AR variants\u003c\/strong\u003e, the 4971B works with \u003cstrong\u003eCommercial, Military, and Hybrid buffer tubes\u003c\/strong\u003e, making it a versatile drop-in component for stock assemblies, retrofits, and spare-parts kits.\u003c\/span\u003e\u003c\/p\u003e\u003cp\u003e\u003cspan style=\"font-size: 14pt;\"\u003eInstallation is straightforward using a standard castle-nut wrench or armorer's tool. Whether you are assembling a complete lower, swapping a stock system, or replacing a worn or damaged nut, the \u003cstrong\u003eErgo 4971B\u003c\/strong\u003e provides consistent fit and a corrosion-resistant black finish in a compact steel package.\u003c\/span\u003e\u003c\/p\u003e","brand":"Ergo","offers":[{"title":"Default Title","offer_id":55109973311810,"sku":"153403","price":9.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0997\/7921\/5682\/files\/hires_c7e629df-1d43-431f-ae8f-39e09e469f28.png?v=1784803424","url":"https:\/\/centerfiresystems.com\/products\/ergo-4971b-castle-nut-ar-15-ar-10-steel-black","provider":"Centerfire Systems","version":"1.0","type":"link"}