Phresh Filter 4x20 Lo-Pro

Does anybody know what is different about the "Lo-Pro" version of the phresh filter? They dont seem to have any documentation on it. The filter seems counter intuitive with the CFM rating.

4"x6" 140 CFM
4"x8" 150 CFM
4"x12" 200 CFM
4"x20" Lo-Pro 125 CFM


Could it possibly mean a thinner bed of carbon leading to a shorter life?
Thanks

Email them and bitch like mad ...as those numbers do seem at odds ..as one would think the smaller the filter the more vacuum thru it..?

ps ..and post back here thanks