A medical needle assembly comprising: a needle cannula having a body and a tip, wherein the tip is disposed at a distal end of the cannula; a feature secured to the body of the cannula; a shield slidingly mounted to the needle for movement between a proximal position to a distal position, wherein the shield comprises: a shield body having a central chamber, a distal end and a proximal end; and a plate secured to the proximal end of the shield body and defining an aperture; wherein, when the shield is in the proximal position, the needle is disposed, at least in part, in the central chamber, and the needle extends through the aperture of the plate; and wherein the aperture is sized to permit passage of the needle body and to prevent passage of the feature; a flexible member having a thickness, wherein the flexible member is fixedly attached to the shield body, wherein the second end of the flexible member is biased radially inwardly into the central chamber; characterized in that the first end of the flexible member is fixedly attached at a connection point to a circumferential wall of the central chamber, and said shield body has a groove formed therein, when the shield is in the proximal position, the needle body biases the flexible member into a groove formed in the shield body, and, when the shield body is in the distal position, the flexible member is out of the groove and prevents passage of the feature. a needle cannula having a body and a tip, wherein the tip is disposed at a distal end of the cannula; a feature secured to the body of the cannula; a shield slidingly mounted to the needle for movement between a proximal position to a distal position, wherein the shield comprises: a shield body having a central chamber, a distal end and a proximal end; and a plate secured to the proximal end of the shield body and defining an aperture; wherein, when the shield is in the proximal position, the needle is disposed, at least in part, in the central chamber, and the needle extends through the aperture of the plate; and wherein the aperture is sized to permit passage of the needle body and to prevent passage of the feature; a flexible member having a thickness, wherein the flexible member is fixedly attached to the shield body, wherein the second end of the flexible member is biased radially inwardly into the central chamber; characterized in that the first end of the flexible member is fixedly attached at a connection point to a circumferential wall of the central chamber, and said shield body has a groove formed therein, when the shield is in the proximal position, the needle body biases the flexible member into a groove formed in the shield body, and, when the shield body is in the distal position, the flexible member is out of the groove and prevents passage of the feature. a shield body having a central chamber, a distal end and a proximal end; and a plate secured to the proximal end of the shield body and defining an aperture; wherein, when the shield is in the proximal position, the needle is disposed, at least in part, in the central chamber, and the needle extends through the aperture of the plate; and wherein the aperture is sized to permit passage of the needle body and to prevent passage of the feature; a flexible member having a thickness, wherein the flexible member is fixedly attached to the shield body, wherein the second end of the flexible member is biased radially inwardly into the central chamber; characterized in that the first end of the flexible member is fixedly attached at a connection point to a circumferential wall of the central chamber, and said shield body has a groove formed therein, when the shield is in the proximal position, the needle body biases the flexible member into a groove formed in the shield body, and, when the shield body is in the distal position, the flexible member is out of the groove and prevents passage of the feature.