The Starline 10mm Magnum Brass is a heavy duty, lengthened 10mm Auto. CANNOT BE USED IN STANDARD 10MM PISTOL. Starline is a family owned business and prides itself on producing the highest quality brass case available. With a production process focused on quality not quantity, Starline makes the finest brass and has for more than 40 years out of their state-of-the-art manufacturing facility in Sedalia, MO.