Prefilter for SteriVex filter

[AussieThunder]

I read that the SteriVex filter requires a "prefilter" before use or otherwise it will clog. What is meant by a "prefilter"?
Thanks.

 

[BigRonWannabee]

Its just a thin sheet of material that has a larger pore dize than your actual filter. If its for a syringe filter than it screws on before the filter. If its for a benchtop filter, it will usually be a circular sheet that sits on top of the filter membrane.

It acts to filter out larger particulate so the actual filter membrane wont clog as fast.