We use commercial grade lead free and flame resistant 18oz 1000D pvc vinyl. 18oz refers to the weight of the vinyl per square yard of material, 1000D, the D refers to The weight of the thread per unit length. The larger the number before D, the heavier the fabric of the same area.。 It is 3 layers pvc tarpaulin which strong fire retardant and water-proof, it is two layer tough pvc tape with one layer polyester fiber net. Except 18oz durable material, we also reinforced high stress points with extra stitching and heat sealing.