A protective sheath (100) for a cannula (210) arranged on a hub (200) which can be fitted onto a syringe (300), the sheath including female elements intended to cooperate with male elements (201) of the hub (200) for guiding thereof, and characterized in that the female elements include a retracted position before use RBU, a retracted position during use RU, and a retracted position after use RAU, wherein the whole length of the cannula (210) is inside the sheath (100), the female elements further include an ejection position E, wherein whole or part of the cannula (210) protrudes out of the sheath (100), and further characterized in that at least two of the RBU, RU, and RAU positions are substantially transversally aligned.
