Its cap is prefilled with 10% neutral buffered formalin and sealed with a resistant membrane.
It is easy to use. Simply open the container and remove the safety ring. Insert the specimen into the empty cup: there will be no direct or indirect (vapours) contact with formaldehyde.
Once the specimen is in the cup, insert the perforator and close the container: the membrane will automatically break, allowing the liquid to be released into the cup. The specimen can be fixed now.
The O-ring guarantees a hermetic sealing, preventing both the liquid and its vapours from coming out of the container.