This Thompson Center Barrel is a factory replacement for the Dimension modular rifle system. The Dimension rifle system allows the shooter to determine what caliber is needed for the current situation and then switch components to create the most suitable platform. This allows one rifle to take game ranging from prairie dogs to moose, and any species in between. This barrel is stamped with the letter corresponding to the series of parts that coincide with its particular caliber. Simply choose the bolt and magazine with the same letter, use the Thompson Center Torque Tool (sold separately) to tighten the barrel, and you're ready for your next hunting adventure.