Shimano 3/16" stainless steel ball bearings in a retainer. These fit all shimano hubs that use the alloy axle.
That includes the
Shimano T780 XT touring hubs,
Shimano XT M78x series and M8000 series hubs and wheels
shimano 6800 ultegra hubs and wheels
Shimano Dura Ace 7800, 7801, 7850, 7900, 9000 series hubs and wheels.
the caged balls are needed for the front hub and the rear DS bearing.