PajamaMania Women's Bamboo Jersey Light Weight Tank with Short Pajama Set 70% Bamboo Viscose/30% Cotton Racer back tank has wide straps and a small gather in middle of back. Classic cut shorts sit at the natural waist and stay in place with an elastic waistband for a comfortable fit. Perfect lightweight material for spring and summer nights The material is made of 70% viscose from bamboo and 30% cotton Sizing Runs as follows: Small (2-4), Medium (6-8), Large (10-12), XL (14-18).