[DIMENSIONS OF PET BACKPACK] Before purchasing, please measure your dog's sitting height (from front legs to the top of the head) to ensure a proper fit. - L Size: 17.4" L x 13.4" W x 10.6" H - Suitable for cats up to 15.4 lbs - For dogs up to 13 lbs with a sitting height of 15.6" or less - XL Size: 19.3" L x 15.7" W x 12.9" H - For cats weighing 15.4 lbs to 24 lbs - For dogs weighing 13 lbs to 22 lbs with a sitting height between 15.6" and 17.6" [EXPANDABLE DESIGN] - Expanded Size: 13.4" L x 24.4" W x 17.3" H - Features an expandable back for additional space, enhancing comfort and air circulation for your pet. - Provides a cozy environment, allowing your pet to move freely and reducing anxiety during travel. [GREAT VENTILATION & COMFORT] - Equipped with four breathable mesh windows for optimal airflow. - Allows you to easily monitor your pet while they enjoy the view. - Multiple entrances for convenient access, while a cushioned bottom with a removable, washable cover ensures a comfortable resting spot. [ERGONOMIC DESIGN] - Widened and padded shoulder straps and back provide support, reducing strain and enhancing comfort during transport. - Two retractable buckles on the top and bottom maintain shoulder strap stability, preventing deviation during use. [SAFETY & STORAGE] - Made from high-quality Oxford Cloth that is waterproof, anti-scratch, and non-irritating for your pet's comfort. - Lock-type zippers prevent accidental openings by pets, ensuring safety. - Built-in retractable hook and rope system keeps pets secure and prevents escapes. - Side pockets offer storage for food, poop bags, and essential accessories, making travel more convenient. [USE SCENARIOS] - Ideal for hiking, allowing your pet to enjoy the great outdoors while being comfortably carried. - Perfect for trips to the vet or pet-friendly cafes, providing security and comfort. - Great for air travel, meeting airline requirements while ensuring your pet's safety and comfort.