ClearBlue Ionizer Controller Settings You need the volume of your pool or spa which you can calculate here. The model number is on the back of the controller. Model: A-400 A-700 A-800 A-850 CBI-350P-SA CBI-350P-SN CBI-350P-18 CBI-350P-25 CBI-350P-40 CBI-350L-SA CBI-350L-SN CBI-350L-18 CBI-350L-25 CBI-350L-40 CBI-350B-25 CBI-350B-40 Pool or Hot Tub Volume: Gallons Liters Go