Campagnolo HB-RE023 hub bearing. Fits all Campagnolo and Fulcrum hubs/wheels that use the oversize alloy axle (17mm) and have cup and cone bearings from about 1999 onwards (except 2015 onward bora/zero front rim brake wheels). The bearing are used in Zonda disc brake wheels too. This is the steel bearing set (not for USB or CULT hubs). The list of compatible wheels is far too long to write.
Supplied is the bearings for one side of the hub only.