M13 link

M13 links reassembled to previously fired 7.62×51mm NATO cartridge cases
M13 links connect up to 200 7.62×51mm NATO rounds contained in an M19A1 ammunition box used to feed an M240G machine gun

The M13 link, formally Link, Cartridge, Metallic Belt, 7.62mm, M13, is the U.S. military designation for a metallic disintegrating link specifically designed for ammunition belt-fed firearms and 7.62×51mm NATO rounds. It was introduced in the mid-20th century. It is the primary link type for the United States and among NATO for the 7.62×51mm NATO cartridge. As of 2017, it has been in use for over 60 years and is used on the Dillon M134D Minigun, M60 Machine Gun, FN MAG/M240, Mk 48, MG3, HK21, MG5, UKM-2000, K16, SS-77, and Negev NG-7, among others. Some countries redesignated the M13 link when it was adopted.