With the beauty and flexibility of the Windham Weaponry Multi-Caliber System, you can now add the powerful .450 Bushmaster caliber to your MCS collection. The Kit includes the MCS .450 Heavy Profile Barrel with Low Profile Gas Block and gas tube already installed; a .450 Caliber 5 Round Magazine that will slide right into the .223/5.56 Magwell on your MCS Lower, a complete .450 Bolt / Bolt Carrier. Assemble the Barrel & Carrier onto your MCS Upper, snap it onto the Lower and you’re ready for the range. All these MCS components are available separately, and all are made in the USA.