It is classified as  'Powder' but it is of Normal Size similar to Tropica, 
Ada and other Aquasoils, i.e, 1-2mm.
Master Soil is a Japanese active substrate intended for planted tanks.The active substrate Master Soil is manufactured in Japan using the latest technology of multi-stage surface sintering. As a result, the Master Soil substrate has excellent absorption properties, very high porosity, which prevents the formation of anaerobic zones and accelerates the colonization of Master Soil granules with large colonies of bacteria that quickly decompose "ammonia" (NH4 +) and nitrite (NO2). As a result, the time between water changes is significantly longer.