It's 16ga and yes, definitely won't work for main power, starter, ground, or anything directly connected to the battery unless its like auxiliary led lighting or similar... I did notice a couple of the colors looked smaller but the reel shows 16ga and looking at it it looks like they used a thinner jacket over the wire for some reason. Red and black were the old style and it was yellow, green, and maybe one other that were the "new" style with the thinner jacket...
If for some reason it measures differently please let me know. I've had issues with this supplier in the past. They were shorting me like 45' per roll before.
Sorry it is two different styles. I'm at the mercy of my supplier on these things.