Picture above on right for size comparison:
Left: 7.62x39mm Russian, Center: 5.45x39mm Russian, Right: 5.56x45mm NATO (.223 Remington)

One Cartridge not a box: 5.6x39mm Russian, Russian production for Barnaul, steel case
and loaded with a  55 Grain JHP (Jacketed Hollow Point) Head-Stamps may vary from picture.

History of the 5.45x39mm Russian Cartridge:
The Russian Government designed and introduced the 5.45x39mm in 1974,
possibly in response to the USA's 5.56x45mm NATO (.223) cartridge used in
the USA's M-16 and AR-15.
Like the 5.56 NATO the projectile is long and slender to provide very good accuracy,
however will tumble on impact for maximum damage on the target.
The 5.45x39mm is used in the AK-74, basically the same as the AK-47, which is
chambered in the heavier 7.62x39mm Russian, both are great military rifles