 USPSA introduced Single Stack as a provisional division under the name "1911 Single Stack" in 2006 and made it a regular division in 2008 under the name "Single Stack".Only single-stack model 1911-pattern pistols are allowed in this division, and they must comply with a maximum weight limit, as well as fit fully within a box of specific dimensions.The equipment rules are similar to Production Division, other than providing for 8 rounds for major calibers and 10 rounds for minor.