This is a standard issue 10-Round magazine for the Barrett MRAD and Mk22 long range sniper rifle, both ASR and PSR. Barrett factory made for small breech. Known as Barrett Type A.
Barrett specifies for .338 Lapua and .338 Norma Magnum. Users also report being able to use for .300 Norma Magnum.
Black plastic polymer construction.
Manufacturer's Part Number: 14077