Winchester Repeating Arms SX4, Hybrid Hunter, Semi-automatic Shotgun, 12 Gauge, 3 Chamber, 28 Barrel, Cerakote Finish, Flat Dark Earth, Realtree MAX-5 Synthetic Stock, 4 Rounds 511304392 The refined SX4 is based on the bullet proof Active Valve System that was the core foundation of the acclaimed SX3. It was 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.