M61 1.0" X 1.0" 0.5HP M61H 1.0" X 1.0" 1.0HP M101 1.5" X 1.5" .75HP M101H 1.5" X 1.5" 1.5HP M151 2.0" X 1.5" 2.0HP M151H 2.0" X 1.5" 2.0HP M303 2.0" X 1.5" 3.0HP M303H 2.0" X 1.5" 3.0HP