PTFE Syringe Filter, AQ™ brand, 0.45µm, 25mm housing, PTFE. Color Code: yellow for 0.45µm PTFE. *AQ™ syringe filters are color coded for membrane type and pore size. 25mm filters are the most commonly used disposable syringe filter size in laboratories with a sample volume of 2.5 ml or more. For smaller sample sizes, 13mm or 4mm devices