I have not used the K wheel, so I have nothing to compare to. I don't exactly know whether I got from Hartville is K wheel.
What I compared to were the OEM coarse wheel from the WC grinder and the 3X coarse wheel that I got several years ago.
Before you order, you can call them and see whether they know the hardness of the 3X wheels they carry.
Hartville is local to me. There is no return shipping if they are not what I want. BTW, currently they have free shipping for >$75 order. (Sorry Stu, you are not included)