These are plastic food storage containers from MUJI (Ryohin Keikaku). They have been used about 3 times, but have some minor scratches from being stored at home. However, there are no problems with their use. Please sterilize them with boiling water before use. Purchasing with other items is also possible. Raw materials: Lid ➡ Polypropylene Body ➡ Polymethylpentene Valve/Packing ➡ Silicone rubber Heat resistance ➡ 140 degrees Celsius Cold resistance ➡ -20 degrees Celsius Capacity ➡ Approximately 1,150ml