FK BRNO Conversion Barrel, 10MM, 5.3, Black, Fits FK Brno PSD, Matte FK-PSD10-KIT Unique auxiliary barrel system that is designed to give the user the option to train with other calibers especially when the stopping and incapacitation power of the 7.5 FK is not required. Our barrel system incorporates a simple barrel change procedure that does not require tools or expertise. A barrel change takes less than one minute