The midsize Patagonia Alvia 22 litre hiking daypack stores your walkabout necessities and features a highly breathable back panel and shoulder straps; extra pockets include externals on the top and the front. Made of rugged 100% recycled nylon. Features and Specifications Built of rugged 100% recycled nylon Comfortable Shoulder Straps Highly breathable Regulator® airmesh shoulder straps and hip belt Back Panel Engineered for All-Day Wear Suspended mesh back-panel construction provides excellent airflow and prevents moisture buildup for all-day comfort Versatile Hip Belt On-the-go accessible hip belt and side pockets secure small items while on the move Rain cover included Sleeve can hold gear and is also hydration compatible Handy Cover Rain cover included 679 grams Materials: Shell: 4-oz 140-denier 100% recycled nylon ripstop. Boot: 4.1-oz 210-denier 100% recycled nylon ripstop. Rain cover: 2.2-oz 100% recycled polyester taffeta. All with a PU coating and a PFC-free DWR finish (durable water repellent coating that does not contain perfluorinated chemicals). Back panel and straps: 100% polyester mesh. Stretch-mesh pockets: 9.4-oz 66% nylon/34% spandex. Lining: 3-oz 200-denier 100% recycled polyester with a PU coating Measuring Your Torso To Determine Your Pack Size Take a couple of minutes to accurately measure sizing will yield the best fitting pack possible. Follow these 3 easy steps:1. Find the Iliac crest (the top of the hip bone)2. Find the C7 Vertebra (the largest bump at the base of your neck)3. Measure from the C7 down along the spine to where it intersects with the Iliac Crest. Use the table below to then determine your correct pack size. Patagonia Technical Backpack Sizing Table  Size Range Suit Torso Length Suit Waist Small / Medium 16"- 19" 28"- 36" Large / Extra Large 19"- 22" 32"- 42" Patagonia Altvia 22 Litre Lightweight Hiking Day Pack with Raincover