Retractable medical device including a body having an open back end and a front end. A movable member is arranged within the body. The movable member has a back end and a front end. A needle holding member is movable to a retracted position within the movable member when the movable member experiences at least one of: the front end of the movable member is caused to expand generally radially the back end of the movable member is caused to contract generally radially the front end of the movable member is caused to expand generally radially when the back end of the movable member is caused to contract generally radially and axial movement caused by a cap closing off the back end of the body which engages a tapered surface of the back end of the movable member.
