How to choose a precise syringe filter: Aijiren disposable syringe filters come in many types. There are mainly two series, one is hydrophilic and the other is hydrophobic series. The syringe filter has two diameters: 13mm and 25mm. The pore size of the filter membrane is 0.22, 0.45um. Membrane materials include: RC, nylon, PVDF, PTFE, etc.