Check the listing for details. RZ Mask FILTER, F1 Standard + Active Carbon Filters (Medium) 3-pack. Condition: New. Listed at 19.88 USD. Contains 3 Filters in sealed original packing never opened Only fits Medium F1 CARBON FILTER L 3PKBrand Name: RZ MaskRespirator Type: Multi-PurposeProduct Type: Replacement Active Carbon FilterSeries: F1Color: GraySize: LargeNumber in Package: 3 pkPackaging Type: BoxedAdjustable Nose Clip: YesReusable: YesFiltration: 99.9 percentQuick Release: YesConsists of two filter layers- the outer particulate filter and the internal active carbon elementTraps particulates as small as .1 micron in size99.9% effectiveCommon uses: Low intensity, fumes/odors20-30 hours of continuous use with heavy dust exposure to things such as grain bins, off-roading, construction/demolition, etc.30-40 hours of continuous use with light dust exposure to things such as grain bins, off-roading, construction/demolition, etc.50-60 hours of continuous use when protecting against allergens, pollutants, odors, etc.