Millipore 250mL analytical vacuum filter holders are designed for filtering liquids for bacteriological or particulate contamination analysis. These stainless steel analytical vacuum filter holders can be autoclaved or flame-sterilized. A No. 8 perforated silicone stopper mounts inside the mouth opening of a standard 1-Liter filtering flask. Complete assembly includes a stainless steel filtering funnel, support frit & base, stainless steel funnel cover, anodized aluminum spring clamp and No. 8 silicone 1-hole stopper. No gasket is required.