53% Polyester - 47% PBT Long-lasting durability Soft and comfortable Chlorine and fade resistant Heat transfer Swoosh The Nike Hydrastrong Solid Racerback is perfect for athletes looking for a classic fit in a modern cut. The regular straps work for a wide range of sizes and activities, providing medium support. The standard bottom coverage is great for all water activities. The full liner and flat seams ensure a great fit without chafing.