More info please... Have you or do you intend to SBR the pistol? (Assume you don't own a registered conversion device for such a basic question... And that's ok). That will help determine if you are looking at a stock or a "brace". If you do indeed want a stock then still more info is needed... Are you looking for a fixed, collapsible or folding stock? You referenced the ATI, so do you only want an F model A3 collapsible? The options are many.