Modular backpack

Piquadro Hexagon Modular Anti-Theft Travel Backpack for Laptop and iPad® - Black, ONE SIZE

Lowepro LP37182-PWW, ProTactic Bottle Pouch Modular Accessory for ProTactic 350 AW II/450 AW II Backpacks, Insulated Construction, Fits 1L Bottle

Stretchable padded, insulated construction - Drawstring toggle for closure and easy access - Attach to ProTactic backpacks or belts via SlipLock - Fits 1L water bottle or canteen and small items - 1 x Lowepro ProTactic Bottle Pouch