Designed for racing at the highest level, the Performance-T is On's ultra lightweight yet Swiss-engineered to the max running top. It features a blend of high-tech fabrics in a stripped-down design for extreme lightness. The tear-proof front is engineered to shield, dry and protect. The back features a highly breathable, moisture-controlling mesh fabric for a refreshing flow of air and running unrestrained. All seams are taped, not stitched so it feels like you're wearing nothing. We wear our Performance-T for race day as well as warm weather runs and fast training.