I bought this JJ Cole Bundle Me to use in my six month old's Chicco Keyfit 30 carseat. The product is very warm, and it definitely eliminates the need to bundle her up in blankets or a big jacket in the frigid weather. The Bundle Me attaches to the seat by wrapping an elastic band around the back of the seat. This attaches a bit awkwardly to the Keyfit, and at first, I was a bit worried that the band would slide up and off. After more than a month of use, though, this hasn't happened. As one point of concern, I don't love the extra flap of blanket that can be pulled over the baby's face or folded down. I feel as though my baby could flip this flap over her own face just by wiggling and flailing around underneath the sack. I'd like to be able to zip up the sack and keep it over her in the car, but with a backward facing seat where I can't watch her, I just don't trust that she won't cover herself.