Product review (2 stars): Did not work for me!
Sorry to say they do not last long, after 3 weeks they must be replaced! New ones I just installed 2 days ago  started to go into the blue area (working properly) now have gone back into the red area (need to be replaced) They are also cut very poorly (not square) Will not buy again! Going back Holmes brand 2 sets of three, lasted all last winter, 4 1/2 months. I also clean the machine weekly.