Product review (5 stars): Replacement orifice works perfectly
We have Carrier Humidifier model HUMCCLBP 2417 (Large ByPass series 24 at 17 gal per day) This is equivalent to the Aprilaire 600 model, just re-branded for Carrier. Our restrictor orifice seemed to be partially clogged, with only a slow drip of water entering the humidifier. I tried to clean it out with a tiny drill bit, but I made the opening too large and then a slow stream of water was pouring out. Time for a new orifice. I ordered this one after checking the specs to determine that my unit requires the 3 gal/hr orifice, which is the yellow one. This fit the 1/4 inch tube perfectly and my humidifier water flow rate is back to where it should be. This is a two-pack, so I now have a spare orifice handy.

Quoting from the Aprilaire Humidifier Service Manual:
"To clean orifice, gently insert a fine needle through the small opening. As an alternative, use a drill to clean out the opening: use a #77 drill (0.018 dia.) for Models 110, 220, 400, 550, 550A, 558, 560, 560A, 568 & 600; use a #73 drill (0.024 dia.) for Models 112, 224, 330, 350, 360, 440, 760, 760A, 768 & 700. If the opening cannot be cleaned out or is enlarged, replace with new orifice (white for the 110, 220; red for the 112, 224, 330; blue for the 350, 360, 440, 760, 760A, 768, 700; yellow for the 400,550, 550A, 558, 560, 560A, 568, 600). Models 445, 445A & 448 have no orifice."