USWF-SW5-2045 is a 5 micron 20"x2.5" string wound sediment replacement filter that is proudly manufactured in the USA. It is made from FDA Title 21 compliant polypropylene string wound around a polypropylene core to provide a high quality filter independently tested to NSF / ANSI standards 42, 61, and 372. String wound filters are typically used in well water applications because they are excellent at handling a wide variety of particle sizes. The string creates a large surface area for dirt holding, and as the string is wound tighter at the core than at the surface it provides great dirt holding capacity for non-uniform sediment. Most private well owners know to avoid using cellulose filters on non-chlorinated well water, but many don't realize that cotton fibers used in many string wound cartridges are made up of over 90% cellulose material. USWF string wound filters are only made with polypropylene fibers, making USWF string wound filters the perfect sediment filter choice for untreated well water. This American made filter is a compatible replacement for other popular string wound sediment filters like the Pentek WP5BB20P, Hydronix SWC-45-2005, and more.