H-141 Magazine Base Pad
Originally made to accomplish 21 + 1 in 40 S&W this one inch add-on to factory magazine can accomplish 21 + 1 in 40 S&W, 24 + 1 in 38 super and 13 + 1 in 45 ACP.
Recently the Tanfoglio factory changed the magazine bodies so capacity is depending on the generation of magazine body you are using.
Also, an aftermarket follower and spring will help accomplish the increased capacity.