Qualitative Grade
| Grade No. | Flowrate | Retention microns | Wet strength | Thickness, mm | Ash % | |
| 4 | Excellent retention of coarse and gelatinous precipitates | Fast | 20-25 | Low* | 0.21 | 0.06 |
*Suitable for gravity or low suction filtration. Care must be taken to prevent rupture of the paper.