What size Wire for box mod?

[Panther1911]

I am going to make my first box mod soon, I will be using a 30A switch for the first one. It will be dual 18650 in parallel. What size wire should I use?

If I wanted to do a 2nd box with the 30A switch in series, what size wire?

I also have some mosfets to make one using a smaller switch, what size are you all using for the power wires?

 

[Midniteoyl]

So, you are gonna build something electrical and dont know how to size wires? Or even find how to? Have you done anything like this before?