They are more of a thick felt, about 1/16” thick, totally opaque/non-see-through but breathable. Just amazon cheapos but i have had great success with them and this type in general. I am always open to better options if you have some. I really like the pots @Atulip uses with the drawstring up top! Wish i could find some of those! Seems like a pretty awesome design
They were called "Royal Pots" I got on ebay a decade ago, but I can't find 'em now. Got like 50 x 3 gallons in a box somewhere lol.