Rock Island Armory Z-Series CS 9mm Luger 3.98in Black Nitride Steel Pistol – 16+1 Rounds – The Z21 CS sports similarities to the barrel lock up of most modern pistols where its barrel and slide are locked together until the barrel is cammed down by a block. You can choose between a cocked and locked capability to use a single action trigger system or a double action trigger system. It has great ergonomics, safety decocker, a good sight attached and finishes off with a frame to slide and barrel fit.