Economical, Autoclavable Funnels for Vacuum Filtration Transparent funnels with graduations permit easy visual measurement. Less expensive than stainless steel and more durable than glass. Tapered stem fits standard size #2 stoppers. Available in 50 and 200 mL capacities. Changing filters is easy. Twistlock coupling minimizes filter tearing. 25 mm polysulfone filter funnels are economical, autoclavable funnels suitable for vacuum filtration applications.