True compression. I'd been looking for a shirt like this for my son with sensory processing issues. The ones I found in the stores were either long enough (to tuck in) and too loose or tight enough but only came down to his belly button. These are deliciously long and delightfully compressive. My son is 6 years old, 50" tall and 51lbs. That's tall and downright skinny. He actually likes the fit of the small even though it fits like a second skin. For most, a size Medium would be perfect. Ordering more today.