If you want to keep your baby dry and warm while in their infant seat, buy this. We have a Chicco Keyfit 30 and it fits like a glove. I bought this set 4 1/2 years ago with our first child after being caught in a downpour and realizing how useless an umbrella is with a car seat. The rain cover is now in use with our third child and still fabulous. The rain just runs right off of it and the cover has a greenhouse-like effect in the winter which blocks the wind and keeps baby warm. It also has the added bonus of keeping potentially intrusive fellow shoppers from attempting to reach in and touch your baby in a store, and if someone's coughing or sneezing nearby I don't worry about it. Because it's clear, you can still see baby at all times.

I leave this on for most of the winter and just unzip and flip the front up when in the car (you may have to move the front of the cover up a bit to clear the car seat locking mechanism so the cover doesn't get stuck in it). If it seems like baby's getting too toasty outdoors (ie a sunny winter day) or in a store I just unzip some on the sides to vent it a bit. Given the time of year of my babies births I haven't used the sun cover much but the rain cover alone makes this set well worth it.