Tightly woven aluminum or steel corrugated mesh screen encased in a formed aluminum frame Screen hole mesh 30 PPI normally Built for ruggedness and durability, cleanable and easy for service Decreasing noise level while creating low air restriction To provide maximum airflow with effective filtering Different finishes are available for cosmetic purposes   MF60S-30N , for 60mm(2.36 inch) Fan MF80S-30N , for 80mm(3.15 inch) Fan MF92S-30N , for 92mm(3.62 inch) Fan Edit Edit Edit MF120S-30N , for 120mm(4.7 inch) Fan MF172S-30N , for 172mm(6 inch) Fan Edit Edit