... 1uniform pores 2it is odorless, non-polluting, easy to use, 3inexpensive and safe Walnut shell filters material1 [pore-forming materials ... pores, and it is odorless, non-polluting, easy to use, inexpensive and safe. Moreover, the pore size of the ... 2.0-4.0mm function:Polishing process of spectecles, jewelry, button, stamping parts, electronic parts, etc. Walnut shell used as polishing material for ...