The first polymer frame model created by Beretta is the Px4. The double action/single action trigger, decocker, and safety configuration of most of Beretta's models were transferred over to the Px4. The rotating barrel is the main distinction from the rest of the series. Other Berettas had a fixed barrel and locking block assembly, while other manufacturers frequently employ a barrel that tilts upward during the recoil cycle. The basic model has a 17-round magazine, but variants of the 9mm Px4 with 10-round magazines are offered in states with legal limitations. Additionally, .40 S&W and .45 ACP alternative chamberings are also available. There are also compact, carry, and subcompact variants. The SD F is a unique model that is suppressor-ready and has an FDE frame and threaded barrel. Cosmetic variations such as the Inox (stainless slide), FDE, and gray versions complete the Px4 line. The Px4 is available in four models: Type C (Single-action-only; Constant Action" - the hammer is in a half-cocked position. Spurless hammer. No decocker. No safety), Type D (Double-action-only. Spurless hammer. No decocker. No safety.), Type F (Single and double-action. Decocker. Manual safety.), and Type G (Single and double-action. Decocker. No manual safety).