I used to buy them for my Cub Cadet,, back in the late 1980's,,
with carbide brazed to the underside, the little sand that the blades would suck up would erode away the steel above the carbide,,
I mowed a LOT of acres with them, and they literally worked as I described,,
The blades stayed mower blade sharp, until the carbide finally wore away, then, I would toss them,,
Back then, the three blades cost about $100,, pricey, but, worth it to me back then,,
That was for the blades of a 44 inch deck.