This Sondico Core Baselayer is great for training sessions, thanks to mesh ventilation panels added to the underarms and a rubberized hem for a secure fit. . . Short sleeves . Crewneck collar . Rubberized trim to the hem . Mesh ventilation panels under the arms . Flatlock seams . Keep away from fire. Shell: 92% polyester, 8% elastane . Mesh: 82% polyester, 18% elastane. Machine washable. Imported. . NOTE: This product is sold in U.S. sizes. While the physical product may display both the U.S. & U.K. sizes on it, please place your order using the U.S. size.