Welding cable sizing shrinks
 

Found article in EVA monthly
"It has been brought to our attention that the diameter of welding cable has decreased substantially in the last year because of the increase in copper pricing.The standard relates to amp capacity of the cable, the ability to carry current with a specific voltage drop over a specified length of cable.
It appears that this change has been quite for some time. The cable manufacturers did not want anyone to know that they were reducing their costs by reducing the diameter and eliminating copper strands".
"Noted also was that 2/0 lugs are now too large in diamter for 2/0 cable so requires drop in lug size for proper fit".

Re: Welding cable sizing shrinks
 

I've been using marine grade battery wire. 4G is still 19mm. There is a custom shop online that is by far less expensive than cart dealers.