100% cotton. Flannel will shrink a little more than the other fabrics because of its heavier weight. A flannel set of pajamas weighs approximately 20-21 ounces.
 
This pajama set has a roomy, comfortable fit. Most people find our flannel PJs to be larger than expected. This allows for a comfy fit and room for expected cotton sleepwear shrinkage, which is approximately 1" in width and length.