Restore flow rates in your MSR HyperFlow Microfilter with a fresh, new Hollow Fiber filter Hollow Fiber filter meets NSF Protocol P231 for the removal of 99.9999% of bacteria and 99.9% of protozoa from beginning to the end of filter life in 'worst-case' water Easily field maintainable with regular backflushing to maintain 3 L/minute, or one liter every 20 strokes, flow rate Weight: 0.8 oz Made in the USA