Made for miso preparation. I hold miso-making workshops at my home in Ota-ku, Tokyo. However, after the miso is made, we've had many incidents where the bags burst due to the build-up of gas during fermentation in the warmer months. To prevent bursting, it's necessary to release the gas from time to time. But, some people find it difficult to do this when they are away on trips for extended periods. Also, when releasing the gas, opening the bag to let the air out can sometimes lead to air entering, which makes it easier for mold to grow, and that's not good. I looked for pre-made products with air release valves, but I couldn't find any, or they were too expensive, so I had them made by a professional. I have a lot of stock, so I'd like to sell them on Mercari. Instant purchase is OK. You can prepare 2-2.5kg of miso with this bag. The valve releases the carbon dioxide gas generated inside the bag. It has a check valve mechanism to prevent outside air from entering. Instructions for use will be provided in the transaction message after purchase (as it will be lengthy). The price is set per number of bags. 5 bags for 980 yen, 10 bags for 1700 yen, and 20 bags for 3100 yen. If you want to purchase a different number of bags than those listed, please leave a comment, and I will create a dedicated listing for you. *The cost of materials and shipping has increased, so I have revised the price. This is the third price increase. Thank you. ***I am selling these continuously. Price negotiations are not accepted.***