The Rock series is Rock Island Armory’s most well-optioned line of 1911 pistols built in the traditional 70 series design with the addition of next level upgrades. Like all Rock Island 1911s, each is built using 4140 ordnance steel on the industry's best CNC machines while being hand-fitted and tested to strict tolerance guidelines for unmatched quality and value. Caliber choices include 45acp, 10mm, 40 S&W and 9mm. Each Rock series 1911 includes upgraded rear sights with front sight options depending on model choice. Skeletonized hammers and triggers with adjustable over travel stop are offered on every model along, with ambidextrous safety on all with the exception of CCO (51857) and CS-L (51585). Combine this with multiple choices in size and you have one of the most versatile 1911 designs you can buy.