Tekweld mask is 95% polyester and 5% cotton. Polyester does not shrink under normal circumstances. Because polyester is made of man-made polymer, which makes the fibers synthetic, the fabric is resistant to shrinkage. If you wash polyester fabric in hot water and then dry it on high heat, it may shrink some, but not a whole lot. Recommend washing in cold/warm water with regular detergent and dry on delicate or lower heat to reduce any shrinking.