Speedo Kids' UPF 50+ Begin to Swim Thermal Swimsuit 80% Neoprene/20% Nylon Provides added warmth and extra water buoyancy UV50+ protection from the sun's harmful UVA and UVB rays Comfortable and flexible material fabric offers optimum mobility Front zip closure with Velcro tab for easy on and off 80% Neoprene/20% Nylon Item tends to run small. Recommend buying one size up.