I've never used them but I do plan on it soon. A cool chick at this nursery I go to explained to me how the roots become air pruned. The fabric materials allow air to flow in and out of the pot. When roots reach the edge of a smart pot, they’re exposed to air and become dehydrated. The dehydrated root tip stops growing and sends out an army of lateral roots. These lateral roots branch out to form a dense network that extracts moisture and nutrients efficiently. Huge root mass, bigger yields, and a bigger plant? Sign me up. I don't know, I got super excited finding out that information.