Made for miso preparation. I hold miso-making workshops at my home in Ota-ku, Tokyo. However, after the miso is made, we often had accidents where the bags would 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 it's difficult for those who are away for long periods, such as when traveling. Also, when releasing the gas, opening the bag to let the air out often results in air entering, which can easily lead to mold growth and is not ideal. I couldn't find any ready-made products with air release valves, or they were too expensive, so I had them made by a professional. I have a large 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 air from entering from the outside. Instructions for use will be provided in the transaction message after purchase (as it's 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 quantity than what is 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 continuously selling these. Price negotiations are not accepted.***