Power rated 100 gph
Unit Dimension 2" Wide x 2.25" Deep x 8.75" Tall
Recommended to use in 10 - 15 gallons aquarium 

Power rated 250 gph
Unit Dimension 3" Wide x 4.25" Deep x 10.50" Tall
Recommended for 40 gallons or larger size aquarium

Power rated 350 gph
Unit Dimension 3" Wide x 4.5" Deep x 10.75" Tall
Recommended for 60 gallons or larger size aquarium

Power rated 550 gph
Unit Dimension 3" Wide x 5.75" Deep x 12" Tall
Recommended for 80 gallons or larger size aquarium