(edit :whistling:, Zenki drum) axles have smaller bearings than the kouki axles, I'm 99% sure all kouki rear ends are discs, and the bearings are way different, something like 20-30% bigger.
I would actually like to know the size of the zenki bearings compared to an s-series axle if anyone knows? They might be the same, when i replaced bearings on my axles for my t-series they were the same as a local corolla funnily enough in bursons listing.