This microfiber material is very stretchy in nature, but what makes it great is the brushed fleece-lined interior.....it's super soft and very warm. The classic crew neck, long sleeves top is so versatile, you can wear it as outterwear, under base layer (long johns), or even as sleepwear. To keep maximum warmth, it is designed to be figure-hugging, with longer bodice and sleeves. As generous-fitting as it is, it's recommended to order one size down.