I’ve seen it mentioned in user manuals for a device. But many Chinese products don’t have proper manuals. One time I sent an email to a Hong Kong company and they told me.
I've also seen it in the product description online.
I have used this below from LPS to Liberty DAC. There's also a place in England MCRU (Mains Cables R Us), really, that makes them, not too expensive. Audio Sensibility are very good, bit more expensive, Steven is knowledgable and a good guy to work with
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