... pores inside the inert ceramic balls. Therefore it can be used not only for supporting and covering ... the materials are different, the user can select the product by their sizes, pores and porosity, or if ... every more 5% constitutes a grade, but 12 sizes by reference to the diameter, such as Φ3 ... ,Φ50, Φ75. The products in other grade and sizes can be designed and manufactured if to the users request. ...