Silicon impregnated nylon material provides great lightweight flexibility for thru-hiking. Protect against afternoon Sierra thundershower or when sitting on just-dampened rocks and ground. Also ideal for wearing on laundry day in a resupply town. A split center and velcro tabs allow for a range of adjustment around the waist. If you are under 5'8 get the medium, if over, get the large, which is 2" longer. The split center and velcro tabs allow for a range of adjustment. Adjustable waist: 24" to 54" for both medium and largeSizing: Medium for folks under 5'8 / Large for folks over 5'8 (Large is 2" longer)Weight: Medium 2.9 oz, Large 3.2 oz.