Fabric and air pots prune roots by air rather than letting them circle the inside of a plastic pot. When a root tip reaches the fabric wall it dries and stops, and the plant responds by branching further back, which builds a dense fibrous root mass instead of a spiral. The trade-off is that they dry out faster and need watering more often.
We carry Geopot, Pot Sox, Rhizo, Nutrifield, THC and Bio Diesel, in round and square, from around $3 for a small pot up to $550 for large-volume beds. Most sit near $16.
Choosing a size. Fabric pots drain and breathe on all sides, so they tolerate over-watering far better than plastic but punish under-watering sooner. If you are moving from plastic, expect to water more frequently for the same volume. Square fabric pots waste less floor space in a tent than round ones. Heavier GSM fabric lasts more seasons and holds its shape when lifted full.