Burlap valve bags are composite valve bags made by multi-layer kraft paper and a film-coating process. They are filled through the valve opening at the top or bottom using specialized filling equipment. After filling, they automatically form a rectangular shape, featuring efficient filling, neat stacking, reliability, ease of transportation, and an attractive appearance. These valve bags are widely used for packaging powdery or granular solid materials such as food powders, chemical powders, fertilizers, synthetic materials, medicines, minerals, and flexible items.