The Stern Defense STERN DEF. PISTOL UPPER 9MM delivers a reliable, ready-to-fire AR-15 SD MOD 4 9MM upper receiver package that blends precision engineering with practical versatility for PCC builds and rifle-style concealed carry setups. Crafted in the USA with a steel barrel finished in Melonite, this 4.00-inch barrel features a 1:10 rate of twist for stable 9mm Luger projectiles, ensuring consistent accuracy and dependable performance across a range of loads. The compact 4.25 x 4.40 x 18.75 dimensions provide a sleek, balanced profile that integrates smoothly with standard AR-15 uppers, while the M-LOK compatibility grants flexible accessory mounting for lights, optics, or fore-end options without sacrificing rail space. With a complete upper receiver assembly design, it supports straightforward installation for builders seeking a streamlined 9mm pistol or PCC configuration that leverages widely available 9mm magazines and components. Whether youre outfitting a home defense pistol setup, a range-day plinker, or a competition-ready build, this upper combines proven materials, precise machining, and thoughtful dimensions to optimize handling, reliability, and practical performance in a compact 9mm package.