Solids: 3.7-oz 100% recycled polyester jersey. Heathers and cross-dyes: 3.7-oz 100% polyester (50% recycled) jersey. Body fabrics have miDori bioSoft for added wicking and softness, and HeiQ Pure odor control. Heather and cross-dye fabrics are certified M's Cap Cool Daily Graphic Shirt - Smolder Blue X-Dye