RG58U Coax. It is easy to find at electronics shops and even ebay. It has a thick solid core copper center conductor and normal (as in not foil enhanced) thick copper braid shield. It's easy to solder, unlike many other types of coax.
I have used Rean, Deltron, and Switchcraft (especially Gold HD 3502AAU) RCA plugs.
I have used Rean, Deltron, and Switchcraft (especially Gold HD 3502AAU) RCA plugs.