Built on success. The SX4 is built on the bulletproof Active Valve system that was the core foundation of the SX3. We built on that solid operating mechanism and improved the balance controls and internal operating components of the SX4 to make it a worthy successor to the SX3. - Features and Benefits - SYNTHETIC STOCK WITH IMPROVED ERGONOMICS A ROUNDED PISTOL GRIP AND TEXTURED GRIPPING SURFACES gives your hands a sure non-slip grip. Full coverage Mossy Oak