6.3 oz/ly (CA), 3.8 oz/sq yd (US), 128 gsm (EU). 100% performance polyester flat tricot micropique. Rib knit collar. Moisture wicking. Snag resistant. Breathable. Tagless. Classic fit. ^ANSI/ISEA 107 high visibility compliant. Due to the nature of polyester, special care must be taken throughout the decoration process. Please refer to product size spec PDF file for more details.