Each leg is 9ga ... made of three 16ga conductors twisted together. It is not SPC, but indeed it is pure silver in real Teflon.
ALL of my wire comes from my cousin Scott, who works in R&D for one of the big cable manufacturers. With him working in R&D, I can tell him what I want, and he can make it happen under the guise of R&D 
Most all of my DIY cables are designs I spec for Scott to build for me.