Product review (4 stars): the instructions are poor showing this)
purchased for a Aprilaire 500. The water line is cheap - while installing the line, it was crimped when sliding it in the humidifier cover slot with visible plastic stress marks on it. So be careful not to bend it too much.  Can't see this lasting more than 2-3 years but for the cost not an issue.
Note: the black inline strainer is to be installed in the line going into the solenoid, not this part coming out of the solenoid (hence that is why it doesn't fit .. yes, the instructions are poor showing this).
will buy again in 2-3 years.