We took our premium tees to the next level by using cotton interlock fabric instead of our tried and true, comfy classic, cotton rib. Cotton interlock is extremely soft, warmer than a cotton rib, and holds the perfect amount of stretch, making it perfect for baby clothes. We had our essentials independently certified with STANDARD 100 by OEKO-TEX® so that you don’t have to worry about harmful substances in your baby’s clothing.