Polymer MDT AICS External Box Magazines for MDT Chassis systems. Also works in many other M24 type chassis and bottom metals. MDT Detachable AICS box magazines are designed to fit the MDT TAC21" ACC" ESS" LSS-XL" XRS 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. MDT put their magazines through vigorous testing. They have used high quality strength polymer with a high glass content to ensure durability and strength. Although not unbreakable" MDT has driven over these magazines with cars and trucks which did not break them.