I too wonder about this. Have a S&W Performance Ctr Shield .45 and its a bear to get last rd. in. Can see with a single stack wanting to have advertised capacity. In competion with Glock 17 used Dawson mag extender and held 21 + 1. Seems folks want to squeeze more rounds in. Guess that's why Ruger LCP went from 6+1 to LCP Mas with 10+1?