Filter for Spirit Dynabrade Sanders (models 59020, 59025, 59035). These filters catch the excess oil/dirt/dust that the sanders may spit out while being used. They also double as mufflers that dampen the sound from the exhaust. Sanders take 4-5 of the filters each and need to be changed out when they turn black (about every two months of regular weekly use). 30 filters per bag, sold per bag.