The Aerios 18 Backpack has a patent-pending interchangeable harness system that allows you to finetune your fit before you start your hike, so you won’t spend every step thinking about your pack. The ultralight, ultra-strong grid pack fabric sheds light rain and stands up to all the drops, drags, and snags a pack encounters on the trail. What's been updated: Updated with a FC0 DWR finish for a lower footprint. Need a different size? Try the larger Aerios 35 Backpack .