These holders for vacuum filtration accept 47 mm diameter filters. the filter support is stainless steel screen

The ring allows autoclaving with a filter in position without stick age of the filter to the support, and also protects from breakage. it has a rim around the upper edge to simplify the positioning of the funnel and to avoid displacement of the filter. And a silicon O-Ring in the avoid

The screen fits between top and base part, and the whole is held together with a practical hand clamp.

The holders are supplied with a silicone lid, but without a bored stopper to fit them onto a suction Flask. Such a stopper must be additionally ordered according to the diameter required. When large numbers of samples are to tested, three or six holders can be used simultaneously buy fitting them on to manifolds.