From what I just read on marineandreef.com I believe all the models are rated for 1200gph here is their write up
Canister Filters: Ocean Clear Canister Filters
The Ocean Clear canister filters provide chemical, mechanical or biological filtration, and are suitable for all freshwater and saltwater fish only tanks up to 90 gallons and ponds up to 600 gallons. Because Ocean Clear filter units are modular, they are easy to link together for any application. Ocean Clear filters are reliable, built to last and are the ultimate in flexibility.
The Ocean Clear filters work well used in series with a mechanical filter (Model 317, 319, 325, 340) placed before the biological filter (Model 318). If using two mechanical filters in series, always place the filter with the higher micron size first so that you trap the larger particles before the water travels to the second filter.
The Ocean Clear filters can also be used in parallel for additional filtration for tanks over 90 gallons and ponds over 600 gallons.