This is the info on the Doulton filters for their gravity system. I believe it is the same system as the Berkey. The crystal quest filters are 1 micron versus these at .9 micron. They're both a far cry from RO which is something like .05, but it seems to indicate that the Doulton removes a very high percentage of most things. Don't have to hook it up to the sink either. Downside is it's more expensive than the crystal quest but possibly not significantly better. Would be intersted in hearing your experience with the crystal quest. Good luck.