Boston Leather Single Mag Holder For 9mm/40cal . Clip. Snapclosure For 9mm Or 40mm Single Mag Puch Accomodates All Popular Single Stacks 9mm And .40 Caliber. Available With Clip On Belt Holder. Plain Black Package Contents: Boston Leather Clip Pouch Single/doub Stack The Boston Leather Clip Pouch Single/doub Stack is a quality addition to the Boston Leather lineup. For more great deals on Pistol Magazine Pouches by Boston Leather please browse our Boston Leather Police & Duty Gear page.