This sleepsuit fastens with little poppers on the front and a zip on the side. This elastic at the ankles helps it to fit really well.
Cotton 95% , Elastane 5% https://www.t-a-o.com/en/collection-newborn/newborn-boy/sleepsuit-pyjama/sleepsuit-with-printed-motifs-mixed-grey-light-bc13-87578.html