The back panel has PALS compatible mounts. You can slip your backpack's side compression straps under the front mounted webbing. This 4 liter model suits all pack sizes. - Main fabric: 500 denier Cordura, 100% polyamide - Liner: 210 denier polyamide - 25 mm wide polyester webbing - Simple inner pocket - Zipper with flap - Inner D ring for clipping small items to - Flat inner pocket at the rear - Bottom and sides are reinforced with a liner fabric - PALS compatible - Grommet and hole at the bottom for draining - 5 year guarantee against flaws in materials and manufacturing Alternative packing examples of use by the manufacturer: - Medium size tarp and accessories - Lightweight puffer jacket, rain wear or poncho - Regular 1.5 liter bottle and more - 0.7 liter food jar - Jetboil stove and one gas cartridge