this is a follow-up to another thread where a small debate came up about Wix filters Beta reporting. long story short i thought Wix was reporting a different way, hence my argument was clarified and i was wrong. i have not yet spoken to the testing guy but i did get a email back from them. i still wish to talk to the guy to inquire about their testing method because it seems odd that they use such a large varying selection of particle sizes and many of them are odd sizes at that: "Thank you for your inquiry. Beta Ratios 2/20=22/40 B2/20, 2 represents 50% efficiency and 20 represents 95% efficiency. The latter numbers are micron sizes. So, B2 =22 and B20 = 40. Filter is 50% efficient at removing 22 micron size particles and 95% efficient at removing 40 micron size particles."