Quantity per package = 2. The 3M™ 60929s mercury vapor cartridge, P100 particulate filter combo is NIOSH approved and has been designed for use with 3M™ 6000, 6500, 7500 half mask series and the FF-400, 6000 and 7800 full face series of respirators. The 60929s protects against mercury vapor & particulates. The swept-back design allows an enhanced field of view and comfort. If you have not performed a Hazard Assessment to determine your filter change out schedule, 3M recommends changing the 60927 within 50 hours of exposure to mercury vapor, in accordance to your well-documented change-out schedule, or earlier if smell, taste, or irritation from contaminants is detected.