Semi-compression; Waterproof: Fully seam-sealed, waterproof Cordura fabric, waterproof YKK zipper; Crescent shape: Eliminate dead space in your pack; Integrated corded mesh that allows you to contain and compress your goods to easily zip up and keep them dry; Lightweight and durable construction: Withstand scrapes and scuffs; External storage pocket: Store miscellaneous items or store your PackStack Pro when not in use; Only available in Tall size in both 40L+ and 60L+