AKADAMA, Iberaki brand.
14L when packed.
Grain size - ±2mm to ±6mm
(3-5 day shipping, direct from supplier is included in the price.)
 
Qualities of Akadama bonsai soil are....
Iberaki brand is probably the best akadama on the market.
The double line is the grading of its hardness. (Triple line is harder but rarely imported)
Akadama bonsai soil is irreplaceable in bonsai care for repotting.
(There is no substitute no matter what you may hear on the internet.)
Akadama is a type of clay granulate with a reddish brown colour
(Akadama Tsuchi = red earth) of volcanic origin and occurs in Japan on the island of Honshu. It is mined in open-cast mines and exported all over the world.
Akadama is highly recommended as a substrate. It's got everything a good bonsai soil needs.
 
What are the advantages of Akadama bonsai soil ?
Akadama offers a good stability for your bonsai after repotting.
Root cells need oxygen.
The open texture and air spaces help the roots to recover quickly and begin
to grow easily into the new soil.
The good permeability of the Akadama bonsai soil brings air into the rootball.
Much less tendency to soil compaction. Akadama remains structurally
stable, even over long periods of time. I have had trees that have been in it for 10 years or more and still the akadama has its granular texture.
The excellent drainage properties of this soil are good against root rot.
Akadama has a high ability to retain nutrients in the bonsai soil once the
 have been applied and it freely allows nutrient uptake by the plant.
The buffering capacity of Akadama works against pH fluctuations and soil acidification.
Akadama is stable, hardly compacts and decomposes slowly. Nevertheless, 
Depending on the quality of the Akadama bonsai soil (soft and hard) it should be replaced after 3-5 years or even longer. I have had some trees in it for over 10 years without detriment to the tree.