The babystudio sleeping bag range is made from the softest of Cotton (BCI – Better Cotton Initiative) for your baby's delicate skin. Just enough tightness to feel safe like they are being held and touched. The fabric has also enough stretch to ensure the baby is able to stretch out allowing their legs and hips to fall into a "natural frog like" position. Your baby's arms will feel free to move around and fall into their own "natural sleep position".