This wheeled carrier is sturdy and easy to assemble, stores flat. Even includes a collapsible food/water bowl. The 35lb size DOES have ventilation \"windows\" on all four sides and above as well as several openings to stuff my monster into. He is not good with other dogs, he thinks he is a Bull Mastiff at 25lbs. so I have to sit with him in the car and get rushed into an exam room. I have tried classes, de-sensitizing him with trips to the pet store...and this is just easier for both of us. The trick is to get them used to the carrier BEFORE you need to use it. If your pet is food motivated as mine is, take it off the wheeled base and throw treats one at a time near it and into it when they are hungry, like right before dinner. They will jump in so fast for the treat they won't have time to be scared of the new box with zippers. Next is to make a game of wheeling them around in the house. After that, no problem, just DO NOT only put them in it when they are going to the vet or they will run from it. Make it a treat experience even to just go wheeling around the kitchen. It is perfect for those of us with crazy or ailing pets, will make trips much easier on both you and your pet....