PTFE Syringe Filters with GD-4 Pre-Filter, 0.22 um, 25mm, Nonsterile, 100 per pack, GD17035 Polytetrafluoroethylene PTFE Syringe Filters with 4 total layers, the first Filter is a composite membrane of 10um glass fiber and 1.0um PP, the second preFilter is 0.7um GF/F membrane media, the last one is 0.22um PTFE, Nonsterile, 100 per pack