|Great filters, I ordered three sets for a total of nine filters. Dates were 1989 - 2003, all in good quality. To the folks talking about cutting the top off, I don't understand, these are designed to be twisted off and it's as easy as opening a two liter softdrink.
To open the filter, simply pop off the bottom seal and then twist off the 40mm female top. I give these 5 of 5, the reduced size and filter restriction is MUCH better than my NBC from 1971.
I use these to cut the grass (live in Alabama, lots of pollen) and it's fantastic. Using them with a Israeli civilian mask.|