Modified 9mm ammunition.. Works in firearms chambered for regular 9mm ammo. A 9mmP (9mm para) slug is larger than that of the standard 9mm slug. Less propellant is used, but it is compensated by having a higher grain and the fact that 9mmP are used at short ranges. Most police SWAT, FBI HRT, and Special Ops teams use 9mmP because it has a higher stopping power, fragments more than a 9mm regular, and usually doesn't exit the body.