Uncle Mike’s Law Enforcement SlimLine PRO-3 Triple Retention Duty Holsters and dual magazine cases are designed for metal or polymer double-column 9mm or .40 S&W magazines. This holster requires one-third less belt space than standard models, reducing bulk and improving wearability while providing the same versatility. The holster offers three types of retention: an internal locking device, a retention strap/thumb break assembly, and an adjustable tensioning device.