Description taken from PBKids website- Durable, functional and oh-so-playful, our Mackenzie backpacks are packed with pockets and straps to keep everything in place. Personalize it with their name or initials for a smart, extra-special touch. BACKPACKS Made of rugged, water-resistant 600-denier recycled polyester. Interior is lined with 150-denier recycled polyester. Yarn-dyed fiber has incredibly rich color that holds its vibrancy over time. All backpacks have adjustable PP webbing straps that are contoured and padded to ensure a comfortable fit; padded back panel adds extra cushioning. Features a YKK zipper closure with a Nickel finish. Exterior side pockets are designed to hold any of our water bottles (sold separately). Our glow-in-the-dark backpacks feature a material that needs to “charge” under bright light for approximately half an hour to glow properly. Glow lasts for approximately three to four hours. The glow effect will become weaker over time.