The carrier includes a see-through top door that opens outward to help get your pet inside with ease. It also includes a side door that opens booth right and left, and can be removed to have the carrier be used as a pet house The carrier attaches to a car seat belt to keep your pet safe and secure while in a moving vehicle. It is even is stackable for convenient storage that takes up minimal room in your home. The Double Door Pet Carrier comes in two sizes. Small is for pets up to 11 lbs. Medium is for pets up to 17.6 lbs.