The cap is pre-filled with 10% neutral buffered formalin and sealed with a resistant membrane. It is easy to use: open the container and remove the perforator, then insert the sample into the empty cup without coming into contact with formaldehyde (neither vapor nor liquid). Once the sample is placed, position the perforator with the tips facing upwards and close the cap. When the container is sealed, the membrane will break, releasing the formalin required for sample fixation. The airtight closure prevents contact with both formalin vapors and liquid and is ensured by an O-ring integrated into the cap.