Custom 8oz 12oz 16oz Aluminium Foil Side Gusset Coffee Bean Bags with Tin Tin and Valve Wholesale Quality Affordable Coffee Bags,PE material: good flexibility, good stretchability, low hardness. One-way degassing valve: After filling the coffee beans, the gas inside the bag can be exhausted to prevent the bag from rising and bursting, and it can also stop the air outside the bag from entering to achieve the purpose of preserving freshness.