ergoPouch 2.5 TOG Baby Sleep Sack – 100% Organic Cotton Baby Sleep Suit Bag for Cozy Baby’s Night – Temperature Control Baby Blanket (Night Sky, 2-4 Years)

It gets chilly in our house at night and my son (2) doesn't use a blanket very well so I decided to look for a warm sack. We had one of this brand from when he was an infant and I remember loving that one, too. I don't worry about him keeping warm in this, it's easy to put on, he hasn't figured out how to get it off, and it's plenty big and will last him a while.