Its unique design, featuring the filter cup and funnel fit, offers flexibility to filter water into bottles with a wide range of mouth sizes, including narrow-mouth bottles such as commercial water bottles, soft-drink bottles, canteens and SIGG bottles. On wider-mouth bottles, such as Klean Kanteen , Gatorade and Nalgene bottles, only the cup is necessary. Effectively removes particulates from water with the use of a durable 40 40 micron screen. Offers flexibility to filter water into bottles with a wide range of mouth sizes Includes long-lasting, SteriPEN Filter Cartridge to remove particles greater than 40 microns. Easy to use; place in bottle opening and immerse in water or pour water through. Versatile and lightweight. Nests for easy storage. Rugged, flexible material allows it to stow away