Well in my 'first peek' thread:
I introduced the Nubatama series stones.
Here I want to go over just one Nubatama stone in the Bamboo series, a 150 grit stone.
Here's some pics:
It's 205x75x50 mm in size - a brick
Sort of burnt orange in color.
And it works like no other coarse stone I've EVER used.
It cuts metal FAST. It dishes SLOW.
It cuts faster than the 120 pro or GS, faster than the synthetic Ohmura and WAY faster than other finer grit stones. Finer grit stones like the Beston 500, Chocera 400 and other 220 and 320 Shapton stones. It leaves a coarser finish than the finer grit stones I mentioned, except the Beston 500 which doesn't give as fine a finish, cut as fast or dish as slowly.
So far it hardly dishes at all. This is perhaps it's most valuable trait. I've used it on a bunch of CPM 154 Addicts to set bevel angles and a bunch of Aritsugu-A's - and I have yet to have any mud from the stone to show for it. Have yet to need to lap it! The same amount of work on any other stone would give me a mud puddle.
Burr generation is RAPID.
I followed it with a Shapton GS 500. It was an excellent combination. I would also consider it as a starting point for going through the Chocera series - following this stone with a 400 Chocera for instance. From there I switched to some natural stones (aoto and Yaginoshima asagi) for these initial sessions with the 'Bamboo 150'
The 150 Nubatama Bamboo is a finer scratch pattern than the XXC DMT or Atoma 140 and is a perfect followup for them.
It is a porous stone. I would suggest soaking it for about 5 minutes first. That fully saturates the stone. You will need to add water to it to keep it wet. It isn't recommended that you leave it soaking as it doesn't require it.
This is a stone for removing metal. It leaves an edge suitable for slice cutting paper or coarse work. Very 'toothy'. It is too coarse for a final finish but excellent for repairs - chips and tips. Strongly consider this stone for work on single bevel knives.
I'm sure there will be many more reviews of this stone in the future