Having a good design is also very important for sleep sack.
Some design features that I find particularly great are the:
– Shoulder snaps and under arm snaps for fit.
– All around double ended zipper that allows for easy diaper changes. We also just unzip it for her in the mornings and pop her in the activity center, and then she’s back down for her morning nap just a short hour later.
– Stroller/car-seat openings for easy transitions.
Woolino sleep sack has two snaps on the top of each shoulder and a zipper that goes around the side and bottom. It is easy to get baby in and out, in many positions: asleep, sitting up, crawling around. The snaps are secure, so I don’t think a baby could undo them.
Same with the zipper, which also hides under a little tab at each end, so the baby can’t get to it easily. The zipper can unzip in either direction, which is very cool. This baby size also has two snaps under the arms which should stay closed when baby is smaller and can be opened once baby is older to make more room for arm movement.
I love how it opens flat, this is great if you are putting baby down asleep. The sleep sack can be flat in the crib and baby can be laid on top and snapped in and zipped up very easily, without waking baby.