The Sondico Base Mock Neck Top uses Optivent technology for breathability and improved airflow. Making this design even more comfortable is the rubberized hem for a secure fit.. . Rubberized trim hem. Optivent technology. Mock neck. Long Sleeves . Shell: 92% polyester, 8% elastane. Mesh: 82% polyester, 18% elastane. Machine washable. Keep away from fire and flame. 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.