From H20 Wear's website: H2O WEAR CHLORINE-RESISTANT WOMEN’S LONG SLEEVE ZIP FRONT AQUA SHIRT, BLACK – Keep the chill off before or after your next water aerobics class or swim workout with this comfy and durable shirt. SNUG FIT – The shirt is sized to fit snugly, which we highly recommend when exercising in a pool. COMFORT AND SUPPORT IN THE POOL – This aqua shirt is designed to support aquatic exercise. It is made of a comfortable fabric and is unlined. SPANDEX-FREE CHLOROGUARD FABRIC – This fabric is specially designed to retain its elasticity with frequent use in chlorinated pools. The fabric also offers 50 UPF sun protection. DESIGNED BY H2O WEAR – The proud pioneer of chlorine-resistant aquatic fitness wear. Each garment is designed to meet the unique needs of people who exercise regularly in the pool. Designed to perform. Made to last.