Product review (1 stars): There service department is incompetent and untruthful , in my case anyway.
They told me this item was a direct replacement for my AprilAir unit. Not true. Requires a 24vac transformer and rewiring the unit.

The Aprilaire 4005 is the correct replacement part for my humidifiers not the one they sold to me,

Aprilaire Model 330 Humidifier
The Aprilaire 4005 Water Solenoid Valve Assembly is a 120V replacement solenoid water valve. known as part number 4005, this humidifier solenoid valve assembly includes a compression washer and nut on the inlet side of the valve.

Which I was told was unavailable By this vendor. They lied or don't know what they are talking about.