Speedo Kids' UPF 50+ Begin to Swim Thermal Swimsuit neoprene Thermal suit provides extra buoyancy and added warmth in or out of the water UV 50+ trademarked "Block the Burn" sun protection from the harmful UVA and UVB rays 80% neoprene and 20% nylon for just the right amount of comfortable stretch for a great fit and optimum mobility Zipper front for easy on and off, with colorful panel design Improved fit so that overstretched product does not decrease the UPF rating Item tends to run small. Recommend buying one size up.