Attributes . Dynamically Balanced Wheels Sizes 10-1/2 in to 24-1/2 in Feature Flat Blade Wheel, Larger Sizes Have Fixed Sheave Drive, Motor Cannot Be Overloaded at any Given Rpm and Horsepower Regardless of Static Pressure Applied to the System, Ratings Do Not Include the Effects of Duct End Correction, Sizes 10-1/2 in to 20 in Have Variable-Pitch Sheaves, Sizes 27 in to 36-1/2 in Have Airfoil Wheel Both Wheel Styles Provide Full Class 1 Performance Range, Values Shown for Blowers are for (Inlet Lwi) Sound Levels For: Installation Type B: Free Inlet, Ducted Outlet . Names