The stone is of good quality. It can be used with water or oil - but not both at the same time of course :) ... What I really want to mention is that Hayneedle has amazing customer service - no joke! My stone was shipped from the mfg. not hayneedle whse and there was a chip on one corner. They said - we can't have that! ... So they took care of the whole matter with NO cost to me and they were very friendly as if I was doing them a favor!
I recommend keeping two stones in your kit. One with a medium grit (around 800 or so) to perform major sharpening jobs, and one with a fine grit (at least 2,000) to tune the edge to a razor-sharp finish. For real pros, a stone with an ultra-fine grit (8,000 and above) will leave a mirror-like finish on your blade, but most cooks won't notice the difference in terms of cutting ability.

It is better to understand the difference in sharpening stone materials before you are going to make any decision. Among the available options in the market today, Waterstone, oilstone and diamond stone are the most common type of sharpening stone. Each of stones comes with advantages and disadvantages. Waterstone and oilstone are available in natural and synthetic models. Synthetic are the most common and easy to find as man makes them. As the use of natural stones (e.g. original Arkansas or Japanese natural whetstones) is has diminished in popularity, they are beginning to rare in the market. Artificial stones have a more consistent particle size and controlled with a tight mechanism in providing high-quality sharpening stone.
Japanese water stones – both natural and synthetic – are known for their superior sharpening performance, not only for Japanese tools, but also on their Western equivalents. The loosely bonded abrasive grit is washed out very quickly, as it blunts during the sharpening process; this exposes new, sharp, particles that can get to work on the blade. Water stones are lubricated only with water! Never use oil!
The DuoSharp Plus stones are nicely sized at 8” long by 2 5/8” wide and have two grits on each stone to maximize value. The Plus in the name refers to an area of continuous grit in the otherwise interrupted grit surface of the stone. This area is for sharpening edges with fine points that might be difficult on the interrupted surface. A coarse/fine DuoSharp Plus stone is a good single stone to start a sharpening toolkit.
An important but often confusing area of sharpening is knowing when you're done with one stone and ready for the next finer grit. On coarse stones it is very easy. When you sharpen one side you will notice a burr forming on the opposite side of the edge. This burr is hard to see but is easy to feel. Very carefully feel for the burr by gently running your hand from the spine to the edge. (Do not run your finger along the knife edge from heel to tip, that's only asking for trouble!) A burr is formed when your stone removes material directly at the edge. The burr will move from one side of your knife to another as you alternate sharpening sides. Make sure you have felt the burr jump between both sides before you move on to the next finer stone. That will ensure that you have sharpened both sides effectively. The finer grits are done the same way but the burr is much smaller. On the finest grits you may not be able to notice the burr at all. Testing the knife sharpness will tell you when you're done. (Learn how you can test to see if your knife is sharp.)
The type of stone refers to the material it is made with. You can find many different types, including diamond, ceramic, natural stone, and synthetic. I would only suggest diamond if you’re planning to be sharpening only ceramic knives. Many of the stones you’ll find on Amazon or other retails are made of Corundum, which is a crystalline form of aluminium oxide. It’s a fine choice for a beginner sharpening stone.
Now you may wonder, if a finer stone produces a better cutting edge why do I need a coarse stone at all? The answer is that finer stones work much more slowly than coarse ones. The amount of metal a fine stone removes with each pass is much less than what a coarse stone removes. If you have an edge with a good shape to it from a coarse stone, this is not a problem because the fine stone doesn’t have to remove much metal to improve the edge. If the edge is dull, it will take many times longer to reshape it with a fine stone than it would with a coarse one.