uxcell a17060200ux0163 2Pcs 6203Z Metal Motorcycle Deep Groove Radial Ball Bearing 40 x 17 x 12mm, 2 Pack

I needed to replace the two NSK (ie Japanese) 6004Z bearings on the crank of a light commercial exercise bike.I was hoping to get NSK or SKF ones, both of which I've used before, but no such luck during the current lockdown. So I took the plunge and tried these instead.All I can say is they looked exactly the same as the old ones, were dimensionally identical (measured with micrometers and a telescopic bore gauge, not just a ruler), and fitted perfectly. The clonking crank no longer clonks, and the bike feels like it did when it was new six years ago.Metallurgically, I've no idea how good they are, and if they give out prematurely, I'll update this review in future. Initially though, I've no worries about them. The bike gets some fairly heavy use as it's in a small privately owned but commercial gym.If I was rebuilding my motor bike, especially the hub bearings, I'd still probably be looking for OEM or genuine ones, but these do seem very good for my needs and I'm happy to recommend them to you.