I put the Cub Cadet blades on mine a couple years ago. There was a choice between "hardened and standard". I went with the "hardened", and paid dearly for them. I do not remember the price, I can't remember what I had for breakfast,
but they were/are WAY better than the cheap one's I had previously.
Looking on Cub Cadets website,
759-3840
BLADE 21"LG QTY-3 H/C (759-3
$162.36
759-3839
BLADE 21"LG QTY-3 (759-3
PRICE$73.56
I know I didn't pay this much, but it was enough...