STANAG
Shortly after NATO's acceptance of the 5.56x45mm NATO rifle cartridge in October 1980, draft Standardization Agreement 4179 (STANAG 4179) was proposed in order to allow the military services of member nations easily to share rifle ammunition and magazines in the interest of easing logistical concerns. The magazine chosen to become the STANAG magazine was originally designed for the U.S. M16 rifle. Many NATO member nations subsequently developed or purchased rifles with the ability to accept this type of magazine; however the standard was never ratified and remains a 'Draft STANAG'.
Read more about this topic: Magazine (firearms)