These boards from Tojiro are made from Paulownia wood. It is considered the aluminium of woods in that is has the best ration of lightweight to hard wood.
As a result these boards are very lightweight but tough, so very supportive of a sharp edge helping retain your blades sharpness. They are also very odorless and resistant to fire, decay and rot.
The boards are 27cm by 19cm and 2cm deep.