What is the average particle size of ultra-fine grinders?

• A. 1 to 20 ¬¨¬®¬¨¬µm
• B. 4 to 10 ¬¨¬®¬¨¬µm
• C. 5 to 200 ¬¨¬®¬¨¬µm
• D. 50 to 100 ¬¨¬®¬¨¬µm