I made this for miso making. I hold miso-making workshops at my home in Ota Ward, Tokyo, but when the weather gets warm after making the miso, there were many accidents where the bags burst due to gas buildup during fermentation. It's necessary to release the gas occasionally to prevent bursting, but some people have difficulty doing so when they are away for long periods, such as during trips. Also, when releasing gas, you open the bag to let the gas out, but if you don't do it properly, air can enter, making it prone to mold, which is not ideal. I couldn't find any ready-made products with an air release valve, or they were expensive, so I had them custom-made by a manufacturer. I have a lot of stock, so I'd like to sell them on Mercari. Immediate purchase is welcome. This bag can be used to make 2 to 2.5 kg of miso. The valve releases the carbon dioxide gas generated inside the bag. It has a check valve mechanism to prevent outside air from entering. Instructions on how to use it will be provided via transaction message after purchase (as it would be too long to include here). Prices are set per quantity. 5 bags for 980 yen, 10 bags for 1700 yen, 20 bags for 3100 yen. If you wish to purchase a quantity not listed, please comment and I will create a dedicated listing for you. *Due to increased material and shipping costs, prices have been revised. This is a repeated price increase.* Thank you for your understanding. ***We are continuing to sell these items. Price negotiations are not accepted.***