Just purchased the large for travel in the coming holidays. May need to update this review afterwards after the traveling is done.But we took this bag out and about before our flight travel to test this out. I use this bag to take my small dog to the vet all the time, he even sleeps in it at night, I bought this because I have a 22lb dog and a 4lb dog. The 4lb dog will be traveling with us, so he's been sleeping in it every night.This bag was able to securely (with shoulder straps on my shoulder) hold my 22lb dog but he wasn't able to stand in it, and it was almost an exact fit. Because of the soft sides he was able to get into it and make a u-turn to face outwards but that was about the only mobility he could do in it. However he's still able to be carried in it very securely and with the weight over my shoulder and the handle I'm able to distribute his weight evenly while I'm walking so it doesn't hurt my back. Carrying him by my hands alone tires me out much faster than carrying him with this bag when he gets tired on longer walks.So about the 4lb dog we have, this bag is way larger than he is but we bought it with dual purpose in mind. So we stuff half the bag with a soft dog throw so it is smaller and he doesn't eliminate himself inside. He enjoys the bag and sleeps throughout the night in it. He hasn't been able to chew it up but he does try to scratch at the mesh lining which has held up. I don't think it would hold if my larger dog were to chew at it though, but that's something I'd have to teach him not to do so its no fault to the bag that it can't stand up to a canine's teeth.We also use this bag in the car to keep the 22lb dog when we are on a drive to keep him safe from rolling all over the place. There is a soft foamy mat that's included which he lies on, and underneath that is a wooden board that gives it its structure. The smaller dog isn't able to fit in there with him while he's in there so the smaller one sits in a dog car seat.So overall the construction of this bag is phenomenal to the stuff I've seen while shopping around at Wal-Marts and Targets. This is pretty comparable to the stuff I see at the Pet stores, but those are pretty pricey so I figure I'd spend an extra $20 and get this one which actually claims to hold up to 40lbs of dog, while those other bags don't mention the weight or they only claim to hold 20lbs max.The design of the bag is simple, has a single point of access in and out, top vents, and a back vent. Theres also a zipper on one of the top vents that allows you to slip just a hand in to comfort your dog while on the road. One single pocket in the rear holds about a leash, some dog bags, and a harness at best. Not much else can be held in this bag, just enough but maybe for some not enough. We need a separate bag for things like dog food and water, and the water/food dish, however, I would think it's torture if we left food so close to the dog.Style, very stylish I must add, I got this bag so that it doesn't stand out much as a dog carrying bag. If you close all the vents than it'll almost look like a large travel duffle to the unsuspecting. It probably wouldn't pass close inspection, but the bag is made of nylon, it looked like a canvas material in the pictures but it's nylon, which is good because my 4lb threw up a few times from being swayed while I was walking and it was easy to clean.I would definitely be buying another one of these, but based on how things are looking it will probably last a good 5 years of moderate use so it'll be awhile.Will try and update after we take this thing to the airport next week and see how that goes.