For what it is, PetPeppy is easily the best dog travel carrier compared to others because it's more sturdy and safe for dogs. While no additional sizes are available of this carrier, you can fit a small or small-medium dog into this travel dog crate but note that a lot of dogs find these crates uncomfortable during long trips, therefore it's best for short distance travel and short flights where you can attend to your dog faster.
PetPeppy dog travel carrier is not waterproof or water-resistant and may be difficult to clean due to its construction and the materials used. The main reason a pet owner would buy this is due to how easy it is to carry it, especially if you have small dogs. The expandable space is also a huge advantage since you can store your dog's toys and other supplies without having to carry them with you, but that obviously makes the crate less ergonomic and expands its sides, which makes it less easy to carry.
This carrier is made of a durable luggage-grade nylon outside and is ultra plush polyester inside. A padded shoulder strap and handle are included so that you can easily carry your pup however you like. The bedding that comes with this crate is washable, and the foam liner is water-resistant, so you know you will have this crate until your pup is grown and much longer.