100% Polyester. Quick-drying and breathable swim shorts help keep your kids dry and comfortable.Drawstring fastening. The swimming shorts with a wide elastic waistband are easy to put on and take off, and you can adjust your waistline freely.Essential swim boardshorts, perfect for various sports and beach activities, including swimming, surfing, diving, running, walking, volleyball, cycling, water skiing, drifting, sunbathing, beach or home, and can be used as gifts for boys.The boy's swim trunks are made of a new 4-way stretch fabric and have UPF 50+ UV protection, which can block 98% of the sun's harmful UV rays.