My cats and I love these carriers! Perfect size for my 11lbs and 20lbs cats. It made traveling through the airport and flying so much easier. The wheels are sturdy and roll smoothly. Best part, the wheels are detachable making under seat storage during flights super easy. I flew jet blue and carriers fit under the seats without a problem. The expandable sides collapse easily and don’t cave in on your pets because of the adjustable mat/liner that adds structure (Velcro on 1 size, soft/plush material on the other). Great quality for the price, I highly recommend getting this.