AmaWoo Safe and sound - The halo sleepsack is a miracle worker! My baby instantly felt content and cozy while swaddled in this sack. I felt at ease knowing the she cannot unravel the sleep sack and get stuck in it ; like she could with a loose swaddle. The sack zips up and allows you to Velcro your baby into a swaddle. You can tuck their arms in or leave them out. My little one likes sleeping with her arms out and it doesn’t effect her sleep .