A proper good ol’ time burlap sack, also known as a gunny sack or a hessian sack. Store potatoes in these, fill them with sand and fortify your home, or use them as a Santa’s gift bag. Whatever you do, it will more convincingly with these.
These are primarily made of jute, however, there can be a linen bag or two among the batch. Jute is a vegetable fiber that is used to make burlap, hessian or gunny cloth used in sacks. The material has been used in Asia for a very long time, and the British folks imported it to Europe in the 17th century. The military has been using these kinds of bags as sandbags for quite a long while. An interesting tidbit of information is that jute is also grown for food. However don’t eat these sacks, they aren’t very tasty.
The sizes can vary to some extent. Don’t convince yourself that you are buying a made-to-measure bag but an invigorating surprise and your customer experience will be a lot more enjoyable. The smallest we saw was 69 x 113 cm (27” x 44.5”) and the largest 94 x 115 cm (37” x 45.5”), but there can be other sizes as well. There are no mini pouches or huge tents though so you will most likely get something in between those sizes.
Used Swedish military surplus. Some have been used more, some less, some even appear unused. These can some frayed edges, old stains, patches, original text, and so on. Nothing you put in here falls through though. So, these are all perfectly usable.