ZCI / RA made steel bearings. Pack of 6, each one contains 8 smaller ball bearings. Suitable for 9mm gearboxes using the common standard 3mm gear shaft.
From what I've seen ZCI and SHS/Rocket bushings and bearings seem identical. Like many Chinese Airsoft products there is perhaps 1 or 2 factories actually producing the product, differences start to emerge with QC levels that each reseller apply.