Mossberg 51600 590S Shockwave 12 Gauge 5+1 (3") 6+1 (2.75") 9+1 (1.75") Interchangeably, 3" Chamber, 18.50" Barrel, Matte Blued Metal Finish, Dual Extractors, Corncob Forend w/Strap, Raptor Birdshead Grip Stock. For the ultimate in shooting flexibility, the 590S Series cycles 1.75," 2.75," or 3" shells. Pick one shotshell length for specific shooting needs, or simultaneously load any combination of those shell lengths. The choice is yours with the 590S