Just a FWIW: if anyone tells you that their wire has greater purity than 99.99% (for example the myth of 'six-9s' copper) turn around and run as hard as you can.Also, the wire material is basic OFC copper that is stranded. All this is decent for what you get. They are generally less expensive (under $150 in most cases, unless you are getting a multi-channel snake or something).
Cardas has a very specific manufacturing method where it uses a very high purity copper
No-one anywhere has copper purity greater than 99.99%. This is due to the facts of extrusion- you can certainly start out with something more pure, but by the time its actually safely in the insulation its no more than 99.99%.
99.99% is what is known as 'OFC'.