I just bought some FireCore 50 wires from Nicks, fast shipping and great place to buy from btw. So I had a little wire that I trimmed off so I figured I would cut it apart and compare it to my old stuff. From left to right FireCore50, Summit 8mm, Balden 7mm, Accel 8mm. Initially you will notice how thick the core is one the FireCore50's compared to everything else especially the Summit wires. The quality of the FireCores seemed to be above all of the rest and was easy to work with. I then unwound the wire from the FireCores and the Summit wires. In one inch of plug wire there is more than 3ft. of wire wound around the core, compare that to the couple inches for the summit
This how much wire is in the visible part
This is the core of the core of the FireCores, it appears to be some type of fiberglass or similar.