The flutter tee is a knit style fabric. They are true to size according to reviews. Most children can wear a couple sizes. If you are in between sizes the smaller of the 2 would be more fitted and the larger of the 2 more room to grow most likely.
A child approx. 23.5 lbs. 33.5" in most 18 months can wear the 12-18 months fitted/"just right" and the S 2T big/loose/longer/room to grow. Another child approx. 30 lbs. 36" fits "just right" in the S 2T and room to grow in the M 3T. A child approx. 39 lbs. 42" in most 4s (some 5) preferred the L 4T more fitted.
*Please note this is last year's version in the photo. It has our Pipperdoodles logo on the bottom right (on the tag this year), has a little more of a turquoise hue, and this year's graphic is a little lower and larger.
Due to the way the flutters are sewn, there may be extra stitching near flutters or loose threads that need to be trimmed.