These 47-mm filter holders feature recessed filter support that provides sufficient clearance so that the membrane will not twist or tear when the funnel is secured. Each unit includes a graduated funnel (either 300-ml standard or 500-mL Wide-mouth), silicone rubber stopper and O-Ring, and a base. The #8B stopper adapts to standard 1-l flasks. Models 06644-72 and -76 have a funnel cover that can be vented aseptically using a disposable syringe filter (included). 43301010 06644-76 has a 300-ml receiver interchangeable with all other models.