MDT Detachable box magazines are designed to fit the MDT TAC21 and LSS Chassis systems, as well as many other M24 type chassis and bottom metals. Manufactured from high quality Polymer and uses a tempered steel spring. These magazines were put through vigorous testing. They're made from high quality strength polymer with a high glass content to ensure durability and strength. Although not unbreakable, they have been driven over with cars and trucks which did not break them. Notes:The magazines are guaranteed to work in MDT TAC21, LSS, LSS-XL, HS3, and ESS chassis systems. They do not work with the following inlets; Ruger American in 204/223/556, Browning X-bolt, Winchester XPC and may require fitting in Winchester Model 70. The following systems work well with MDT magazines, but fitting may be required in some cases. This magazine will accommodate 300 Blackout and .204 Ruger cartridges but may require feed lip adjustments and modifications to the internal ribs.