I have a Kia Soul, that means it is a small car. With that said, it actually has a lot of interior room, well until we load in the dog (beagle) and extremely overweight and old cat (stray). The cat demands that she have her large, wire carrier to ride in, the dog doesn’t care. However, that takes up almost all of the room in the back. That is where this roof bag comes in.The bag is very well made of vinyl and tight zippers. Over the zippers is a flap that is velcro’d down. The interior room is large, I would say the stated size of 15 cu ft is very close to the size. For me, this will fit inside my roof racks nicely and will attach to them. I will not be attaching these to the inside of my door panel, as suggested by the directions, as I have no intention of loosening up the door seals.There is a piece that is supposed to protect the bag from the car top, but my roof rack has a base and rails on all 4 sides, so I won’t be using the insert piece for that. For me, this product is well made, well designed and should meet my requirements. In about a month we are going on a 2,000 mile trip so I will update after we return from that.For now, I give this 4 stars, as I cannot say how well it will work out and last on a long trip. I will return to this review in 6 months or less to give an update. For now, it looks like a pretty good buy.Note: I have been an Amazon customer for almost 20 years. I write all of my reviews to reflect my personal observations and opinions on a product. It matters not if I have purchased the item myself or if it was provided to me for review. My goal is to provide other potential customers as much real-world knowledge as possible to make an informed decision. In most cases I will return to my review in 6 months or less to see if I should alter my original observations. In no case will the cost of a product influence my opinions at all. In addition, I will try to include multiple images and or videos on each product, if practical.