There will be a number on the bearing just match that up with a Fag or NSK brand, sealed or unsealed bearing unit, won't be much.My mains-powered Katsu die grinder is getting very noisy and rough - I suspect there might be a bearing on the way out. Their web site (AIM tools) doesn't list any spares for it, though I might email them to check. I've had it since 2019 and it's had quite a lot of use, but I'd still rather spend a few quid on a bearing than £40 on a new one, which will inevitably creep up to £50 for the brushless version.