Shapton Glass Stone, 500 Grit, Double-Thick, #50106.
210mm x 70mm, 10mm thick (total thickness is 15mm: 10mm of abrasive bonded to 5mm glass plate).
Comes packed in a Pro/Kuromaku style plastic case which can also double as a basic stand (though a proper heavier holder is strongly recommended).
This is a special double-thick version of the very popular 500 grit Shapton Glass Stone. If you do a lot of sharpening, this is a great choice to get extra life from this excellent coarse stone.
Shapton GlassStones are very fast cutting and long-lasting. The ceramic abrasive is permanently bonded to a glass plate so the whole unit is very flat and very strong. The abrasive is extremely consistent and dense so you have a great feel and can produce very precise and clean edges, plus these have the convenience of splash-and-go sharpening (do not soak these stones).
The Shapton stone holder (sold separately) is designed to fit these stones perfectly and is quite heavy and tall, providing a great workstation. The more affordable Naniwa universal/adjustable stone holder also works fine for these stones. The Naniwa rust eraser is also popular for quickly cleaning your stones of embedded metal particles.
Of course you'll eventually need to flatten your stones too, so consider one of the Naniwa flattening stones for a great budget solution, or one of the DMT or Atoma or Shapton diamond lapping plates to get your stones super flat.
Made in Japan.
Be sure to check out the Shapton FAQ.