HGS thickness vs stock UIM ground strap thickness
 

Here is a cross section of the HGS wire vs the stock UIM ground strap.

made uim from long HGS wire
 

by the way, I just cropped the end of the longest HGS ground wire to make a new UIM ground. Also, I will crop the next longest to make a new muffler ground. Even with them cropped they are plenty long for our small engine bay.

what gauge wire is the hgs kit? 4 or 8?

i don't know, they do not specify..... all of the marketing material just says 'thick gauge' I am sure you could measure it but I don't have a gauge meter here :-)

Looks like 8 gauge to me. I used 8 gauge monster cable on the UIM and will be using it on the catback. 4 gauge from the negative terminal, soon to be upgraded to aught-gauge, since a friend of mine with a BRDT (Big Red Diesel Truck) is getting a spool for a winch. How much does the HGS cost?

i purchased my kit for $103 from the maker:
http://www.sunautomobile.com

the rx7store also sells the kits:
http://66.216.67.51/product.asp?0=209&1=348&3=650

here is my thread with more pics:
https://www.rx7club.com/forum/showth...hreadid=140153

Welding cable has many small strands , this works very well . The covering will take the heat .You need to solder the end connectors . easy easy