The SD501 - the only water machine worldwide to be certified as a medical device and available on prescription (in Japan) 
There is no other machine of this type certified and used as a medical treatment device in any other country. While other companies have made claims about being medical devices, they could not produce the actual certification. Enagic does have the certificates, complete with certification numbers, so there is no doubt about their credibility.In fact, “Enagic is the only company in the entire water purification industry whose products have been endorsed by the prestigious Japanese Association of Preventative Medicine for Adult Disease. Kangen™ Water Systems is also the only water-related technology that has been officially recognized for its health merits by the Japanese Ministry of Health and Welfare (the equivalent to the US Food and Drug Administration).”
For this reason (each company with a Medical Device certification must manufacture and repair all of their own machines to receive and maintain this accolade), “Enagic does not outsource anything. They make everything from the plates right down to the styrofoam packaging” and thus have “total quality control on every item from start to finish. Each machine is hand-built by a SINGLE experienced craftsman. He is accountable for the quality of the machines he builds.”