Speedo Kids' UPF 50+ Begin to Swim Classic Swim Vest UV50+ Block the Burn protection from the sun's harmful UVA and UVB rays . Soft, durable neoprene construction for warmth and buoyancy Full Front zipper for easy on and off Safety strap with buckle closure Sizing - MEDIUM: Ages 2-4 Years (Weight Capacity: 33-45 lbs), LARGE: Ages 4-6 Years (Weight Capacity: 45-60 lbs)