NWA 400 was found before 2000. Several hundred stones were recovered from the small 1km by ½ km strewnfield located 12 km from the oasis and village of Oum Rokba. Oum Rokba was the name originally given to the meteorites and it is an accepted synonym in the Meteoritical Bulletin Database. A total known weight of more than 95 kg was found. Meteorite specimens range in size from a few grams to 15 kg.
NWA 400 is an H5 chondrite. Even weathered pieces retain significant nickel-iron metal sometimes in patches across slices. Most of the recovered pieces have a smooth exterior surface with no remaining fusion crust.