Super famous blacksmith from Niigata, Iwasaki Shigeyoshi has tested these stones over and over trying to perfect the performance. He rejected the prototype so many times saying it is too soft, by the time he gave a go sign, it was very hard.
When Shapton stones are great with softer carbon steel, Sigma Power stones goes great with any kind of steel soft to hard. This is why I recommend this brand the most.
#120 Small size (210 x 63 x 33mm): 3800JPY, Large size (205 x 75 x 55mm): 6200JPY