The Exhaust Fan Flow Meter is designed to make quick and accurate measurements of air flow through residential exhaust fans. Smaller, lighter and easier to use than conventional flow measuring hoods, the Exhaust Fan Flow Meter was specifically engineered to measure air flows down to 10 cubic feet per minute (cfm). The effective air flow measurement range for the Exhaust Fan Flow Meter is 10 to 124 cfm. When used with TEC’s DG-1000 and DG-700, the accuracy of the exhaust fan flow measurement is +/- 10%. Metering Box inside dimensions are 13″ x 16″ x 8″ (deep).