Doulton OBE. (made in England). This model has a diameter of 2 inches. These will fit our standard size housings. This Ceramic Cartridge is rated at 2 liters per minute flow and is suitable for all water sources. If you are on an untreated water supply and do not use a Viqua UV system we strongly recommend the use of this top quality Ceramic cartridge as a minimum for ULTRA Safe drinking water. Suitable for 10" STD size housings. E-Coli, Cholera, Shigella, Salmonella, Klebsiella, Cysts, Giadia. Please note we still recommend that this filter cartridge has a minimum of 40 PSI water pressure and must have a 1 micron prefilter to protect it from sediment prematurely blocking it.