Product review (5 stars): Quick, easy replacement
This replacement part worked great in my Aprilaire 550. It did come in the reverse water flow position than what my unit needed. But that was easily changed by loosening the nut, turning the solenoid 180 degrees, then re-tightening the nut. The mounting screws were in the right position for mounting on my unit. So even though it looked a little different from the one I was replacing it with, all the couplings and mountings were to spec. And as some have noted, it already had a strainer mounted into the input side so there was no need to purchase that separately. It's been running just fine for a week now so I'm pretty happy with it at this point.