I'm no expert...,
Verified Purchase(What is this?)
This review is from: Silverline CB14 Combination Sharpening Stone 200 x 50 x 25 mm (Tools & Hardware)
...but my knives are a lot sharper after using this little baby to grind them once in a while. In between I use the steel (rod) in my knife set to unroll the edges (I'm sure my wife planes doors with them when I'm not looking).
One thing that I have found to make a difference in the length of time an edge is retained, is the use of a good leather strop in conjunction with the sharpening stone. You can get them on Amazon too - but I was given mine.
Also - if you're unsure about how to go about sharpening a knife - youtube has a wealth of material that you can check out.
The case is cheap plastic - but mine is still working and it has holes that you can use to screw it to a surface if you desire. I don't bother.
For the price, I've got massive value out of this stone; it was worth it just so I can slice my tomatoes nice and thin again! I'd recommend it.