Shapton KUROMAKU "Wine" Waterstone, 5000 Grit

These Kuromaku/Professional series stones are very fast cutting and long-lasting, offering nice sharpening feedback while still being very hard so they resist dishing nicely. Note that these are splash-and-go, so do not soak these stones.
These stones come in a convenient plastic case that also doubles as a stone holder, though the affordable Naniwa universal/adjustable stone holder also works fine for these stones and will certainly be more stable and secure.
Made in Japan.
Be sure to check out the Shapton FAQ.
You can see this stone in action in Shapton's Beginner's Guide to Knife Sharpening video!