I have had other pairs  of these pjs- yes sizing is a bit screwy- I wear size 12 amd medium fits fine . Thicker  fabric than on a long sleeve pair bought at same time.  Ive never had problemwith stiffness, somone mentioned, as they get softer after washing . Love that you can get a real  pair at reasonable cost . I have 5 pairs of these pjs, so its for sure Inlike them !