mercurial hat. the nike true mercurial adjustable hat provides a custom fit with a snapback closure and celebrates the small-sided game with premium embroidery.. benefits. six-panel design with interior taping for comfort. lightweight fabric for comfortable coverage. snapback closure for custom comfort. eyelets enhance airflow. product details. fabric: body: 100% polyester. back of front panel: 92% polyester/8% cotton. underbill: 100% cotton.. hand wash. imported.