These swim diaper shorts (sizes 12 months to 4t...10 to 40+ pounds) are worn as a bathing suit and are a perfect match to the Cwear sun protective swim shirts. The reusable swim diaper shorts are proven to significantly reduce the risk of deadly E. coli bacteria being released into water by infants and toddlers who wear them. Sizes 12 months to 4T...12 months:10-15 pounds, 18 months: 15-20 pounds, 2T: 20 to 30 pounds; 3T: 30 to 40 pounds; 4T: over 40 pounds.