... 1uniform pores 2it is odorless, non-polluting, easy to use, 3inexpensive and safe Walnut shell filters material1 [pore-forming materials ... economic and durable and so on.Uses: It is used for oil field, refining, environmental protection, chemical industry wastewater treatment ... of spectecles, jewelry, button, stamping parts, electronic parts, etc. different size Walnut shell used as polishing material