Davy, I think there MUST be a typo there, as you say .04 is just a tad fine!!! :?
I was under the impression that it was below 1 micron that was most dangerous ( lets not get too techie here), so personally I probably wouldn't be interested in anything that could'nt do below that especially as again you point out most modern extractors do 1 micron anyway.
Though... I suppose that if you have a basic bag system that is the "traditional" 5 micron, then anything must be an improvement. But Then I think I 'd sooner upgrade the filter anyway...
Am I rambling here? :shock: Quick, another glass of wine... :roll:
Mark