Removing particulates before you purify your water with SteriPEN's UV technology is highly recommended and makes for a much more pleasurable drinking experience. The SteriPEN FitsAll Filter effectively removes particulates from water with the use of a durable 40x40 micron screen. 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.?? Water can be poured through the FitsAll Filter or you can submerge the combined FitsAll Filter and bottle of choice. The FitsAll Filter cup also serves as an adapter that allows the SteriPEN Journey or Classic to be used with these wide-mouth water bottles in the inverted position. Weighing only 65 g (2.3 oz.), the FitsAll Filter is made with rugged, flexible materials that allow the filter to be squeezed during storage and return to shape when unpacked. Nested storage dimensions are 88mm (3.5 in.) x 95mm (3.7 in.) x 72mm (2.8 in.).