Ribbed swim fabric Wide cross-back straps Fully-lined Snap buttons for diaper changes on sizes 0-6M to 18-24M NO buttons on sizes 2T to 5-6T Outer: 82% terylene 18% spandex Lining: 95% terylene 5% spandex Sizing: Our one-pieces fit true to size. We suggest buying your child's current size. Keep in mind swim fabric has stretch but also becomes looser when in the water. We designed our swim to fit snug. You can size up one size if at the end of a size range, but we do not recommend sizing up several sizes above your child's current size. The best way to find correct sizing is to choose a similar item (preferably swim) that fits your child well and measure that piece laid flat. Then compare them to our measurements.