There are four KX Matrikx Carbon Drinking Water Filters that you can choose from. Any of the following would be a great choice for you application:
The KX Matrikx 01-425-125-20 Carbon Block Water Filter:
http://www.waterfilters.net/KX-Matri...r_p_0-408.html
The 01-425-125-20 KX Carbon filter is a 0.6 Nominal Micron filter and a 2 Absolute Micron Filter.
The KX Matrikx 02-425-125-20 Coconut Shell Carbon Water Filter:
http://www.waterfilters.net/KX-Matri...r_p_0-417.html
The 02-422-125-20 KX Carbon filter is a 2 Nominal Micron filter and a 5 Absolute Micron Filter.
The KX Matrikx 06-425-200-20 Carbon Block Water Filter:
http://www.waterfilters.net/KX-Matri...r_p_0-528.html
The 06-425-200-20 KX Drinking Water Filter is a 0.5 Nominal Micron Filter and a 1 Absolute Micron Filter.
The KX Matrikx 32-425-125-20 Carbon Block Drinking Water Filter:
http://www.waterfilters.net/KX-Matri...r_p_0-532.html
The 32-425-125-20 KX Drinking water filter is a 5 nominal micron filter and a 10 absolute micron filter.
Depending on the specific contaminants that you are trying to remove from your water you can choose from any of the above filters. If you are using a carbon filter like any of the above to remove contaminants from your water it might be a good idea to have a sediment filter prior to your carbon filter.
You can find the 20-BB housing for these filters here:
http://www.waterfilters.net/culligan...20_BigBlue.htm
You can find a wide selection of sediment filters here:
http://www.waterfilters.net/culligan...h-Big-Blue.htm