Abstract: A sealed container opening, intended for fluid communication with a container for storing medical fluids, comprising a tubular sleeve-formed part (22, 22A) having a resilient pierceable stopper (24, 24A) inserted in its mouth (21, 21A) and a covering sealing device (10, 10A). The sealed container opening contains the same autoclavable polyolefinic material as the container. All parts of said container opening, exposed to the fluid or fluid handling devices are sterilized in a single process by means of steam transferred to these parts during its autoclavation. Saddle formed port systems attachable to a flexible containers are also disclosed.