Instantly loads all six cartridges into any revolver, securely holds rounds until released with a slight twist of the knob. HKS Speedloaders have been proven by decades of use in law enforcement.Specifications and Features:Manufacturer Number: M3-ACaliber:.38 Special and .357 MagnumRounds: SixFits: Colt MK III, MK V, King Cobra, Lawman, Trooper, and Official PoliceRuger Security 6, Service Six and Speed 6 Does not fit: Cobra, Agent, Diamondback or Magnum Plus.