Am astonished and impressed that our senior - and very contrary - cat continues to eat these where all other brands have been 2-day wonders that inevitably ended up as gifts to our friends' cats. Fussy is not the word for him..! Not sure exactly HOW it controls his hairballs, but I must admit I seem to be scraping less of the blessed things off the rug/carpet/windowsill (or where ever else he decides to leave them for me) these days, and far less frequently than before. Bless. If only they could manufacture something that would control the cat as well as the hairballs... Senior Hairbrain control would fit the bill perfectly.