65L is the biggest, standard Ariel Backpack from Osprey On-the-Fly shoulder and hip adjustments ensure a custom fit LightWire frame with breathable Airscape back provides stability DWR fabrication includes rain cover for greater weather protection Compression straps ensure a secure load Pocketing and straps offer storage for sleeping bags, pads, ice axes, trekking poles, water bottles, and more I needed my backpack on time and didn’t see it had shipped for my trip. Called and my backpack was promptly overnighted to me.