Short version: Wow, does this thing work wonders on a double-coated cat!
When the Furminator™ pet comb first came on the market, MomRed got one. It worked OK on the cat, very well on the furniture. The black comb with larger teeth seemed to get more fur out of Athena’s two layers of pelage. However, over time, she became less tolerant of the black comb. [As I’m typing, she’s begging for treats.] The Furminator™, however, she would put up with. This became more and more important, because her arthritis makes it hard for her to reach all the places that need to be groomed and tidied.
Enter Furminator 2.0. The new and improved version has slightly different teeth, and a built-in device that slides forward and cleans the fur out of the comb. Mom got one the day they became available around here.
Athena T. Cat came back from the groomer that day. The groomer and DadRed had to tag-team the cat in order for the groomer to use the clippers and shave off about half the mats. They stopped then, because Athena was getting very stressed (so were the humans). Mom then began working on Athena with the new Furminator™ at home. The picture above shows the results, and is from the third time that day Mom had combed the cat. The clump of fur closest to the camera has been compressed to about the size of my palm. The other was just removed from the cat, and dropped off the Furminator™.
The thing works beautifully. Athena tolerates it. We are getting enormous amounts of fur out of her, which is good, because she is “blowing” her undercoat (as Maine Coons do). The cat is happier, the people are happier, and the gizmo is easy to use with a good, ergonomic grip.
Two paws up, highly recommend.
UPDATE: If you want to see the product on the Furminator site, with reviews: https://www.furminator.com/products/deshed/cat/undercoat-deshedding-tool-medium-large-cat-short-hair.aspx
FTC Disclaimer: This item was purchased for personal use and no one in the household received any remuneration or benefit in exchange for this review.
Cat Rotator's Quarterly 
Brings back some memories. Lily like a curry comb (wider tooth to get the mats and to groom two-layer coat (Russian Blue). Didn’t have to clip out near as many mats with that, cat was less stressed. It DOES bear an uncanny resemblance to sheep shearing, though.
They work a treat. I’ve been impressed with them.
That said, an old fashioned curry comb works wonders for stripping an undercoat. (Probably not so useful on cats, just because of relative size. But on large dogs, it’s a back saver.)
For heavy mats, there’s a comb that has claw like serrated blades for teeth. It looks terrifying, but it works phenomenally well.
Ah yes, blowing coat… GSDs were bad about that, but the worst was a neighbor’s Akita… I swear you could have shaved that dog and it would STILL have shed five lbs of fur!!!
(Looks at the five St. Bernards around the house.)
Akita, huh?
I’ve told my wife that she needs to take up knitting. We’ve got too much spinnable material in the house for her not to take advantage.
(She responded with rude noises.)
Sissies, try seven Newfoundlands. Dog hair is a condiment in this house, and the only place we’ve not found one is inside a egg.