The Pentek DGD-5005-20 water filter is a dual gradient density filter. There are two different densities within one filter. The first stage of the Pentek DGD-5005-20 provides 50 micron filtration. The second stage of the Pentek DGD-5005-20 provides 5 micron filtration. With the DGD Series filters you get two micron ratings for each filter. The DGD-5005-20 can be found here:
http://www.waterfilters.net/culligan...GD-5005-20.htm