Girth gain; what is it

I’ve been wondering, if your girth increases through jelqing, is it just the veins and “blood chambers” getting bigger? Or is there something else increasing too?
So do girth gains always come with more visible gains and is that also the reason girth gains are never insanely big?

I also notice the base of my penis is more girthy than the rest ( maybe little more than before PE, but not sure) can this be explained?

Someone?

Tissue growth.

You’re increasing the capacity of the CCs (blood chambers) mostly. This requires stretching the tissue surrounding the CCs and any other tissue that needs stretching.

Base girth increases are common. Clearly jelqing is going to have less ahead of the grip effect here but stretching probably does (even stretching in the process of jelqing).