It's SOOO soft! The packaging says that the "Plush Dot Velboa: Wicks moisture and breathes so there is less overheating. Lined with lightweight Jersey for extra comfort." All I know is that I'm tempted to leave it on after my 2 month old gets up in the morning because it's so soft to snuggle with!It has no sleeves. Both my babies were/are finger or hand suckers, they need to reach their hands to self-sooth in the middle of the night. The other SleepSacks I've tried have all had sleeves and after putting the SleepSack on over their pajamas they couldn't move their arms enough to reach their mouth.. actually, they couldn't move their arms at all (think Maggie from 'The Simpsons' when she is in her snowsuit). The HALO SleepSack is sleeveless so the baby can still move their arms around which has worked out MUCH better for us.The HALO SleepSack has an inverted zipper. At first I thought to myself, "What is an inverted zipper?" Basically the zipper starts a couple inches below their chin and you zip down. Brilliant for middle of the night diaper changes, plus the zipper won't catch on their chin and it's harder for them to unzip themselves. .