Navy blue plush carpet, 9 years old, 3 dogs, "steam cleaned" by a so-called professional in the 3rd year, vacuumed occasionally, pet stains spot cleaned over the years as I found them. That's the challenge I had to work with. This product worked very well on relatively fresh vomit stains with my new Bissell Deep Clean ProHeat 2X Professional Pet Upright Carpet Cleaner | 17N49. I had spot cleaned them immediately, but some stain remained. The shampoo thoroughly removed the stains without a trace. That said, however, my carpet has some old, "hidden" urine stains. For these, the product needs some help. I used Bissell's Professional Pet Stain and Odor Removing Formula | 77X7 to pre-treat the carpet, letting it sit overnight under damp towels. Then, when I shampooed the carpet, I added Oxy Boost Carpet Cleaning Formula Enhancer | 1405A to the formula. This process made my carpet beautifully brighter, and removed most, but not all, of the old stains. I'll try the same procedure again to try to remove the remaining old stains. It's possible, though, that some stains are there to stay. In summary, the 2X Pet Stain & Odor Formula (60 oz) | 99k52 works exceptionally well on a reasonably well maintained carpet with only relatively fresh stains. For really tough stains, it will need help as described above. The formula is very good and I'm happy with it. I gave it 4 stars. I would have given it 5 stars if it had miraculously removed ALL of the really old, tough stains on the first try, but Bissell doesn't promise miracles. :-) In fact, of the Bissell products I've used, following their instructions and suggestions, every one of them works as described. Bissell makes no false or misleading claims at all. You can buy any of them to suit your needs with complete confidence.