This diamond whetstone is the medium of the range offered by James Barry Sharpening. It is an excellent mid-sized stone with a good width required for sharpening knives (moreso than the 6" stone) without being as large and expensive as its 8" counterpart.
You are purchasing:
1 x 7" by 2 1/2" Monocrystalline Diamond Whetstone
James Barry developed his diamond whetstones to be of the highest quality. They are monocrystalline - which are far superior to their cheaper, polycrstalline counterparts; and they are electroplated to their base block (which is produced to be as flat as possible) instead of being impregnated/glued on.
Both of these considerations give these diamond whetstones an enormous longevity advangate over cheaper alternatives. If you look after your stone it should last you a lifetime.
These diamond whetstones come with a 5 year guarantee as standard as long as they are used with lapping fluid to lubricate the chisels being sharpened, and not oil or water.