A needle assembly (100, 400, 500) comprising: a needle hub with a needle having a needle tip extending from a distal end of the needle hub; a catheter tube attached to a catheter hub having a body comprising an interior surface defining an interior cavity, the needle extending through the catheter tube and the needle tip out a distal end of the catheter tube in a ready to use position; a valve positioned in the interior cavity of the catheter hub, said valve comprising an outer perimeter, at least one slit and two or more flaps; a valve opener sized and shaped to open the at least one slit to open the valve, said valve opener comprising a nose section (150, 430) having an activation end (166, 436) and a continuous perimeter section, two plunger elements each having two lengthwise edges, two stabilizer elements (253, 444) connecting the two plunger elements to form a stabilizing ring (255, 456), a holding space (155, 720) between the two plunger elements, a first through passage (61, 448) located between the nose section (150, 430) and the stabilizing ring (255, 456), and a second through passage (61, 448) located between the nose section (150, 430) and the stabilizing ring (255, 456); a needle guard comprising a resilient arm (288, 290) located at least in part inside the holding space (155, 720) of the valve opener, wherein said needle guard comprises an elbow i) projecting through the first through passage (61, 448), ii) projecting through the first through passage (61, 448) and in contact with a perimeter (65, 708) of the first through passage (61, 448), iii) projecting through the first through passage (61, 448) and in contact with the interior surface of the catheter hub, or iv) a combination of projecting through the first through passage (61, 448) and in contact with the perimeter (65, 708) of the first through passage (61, 448) and the interior surface of the catheter hub. a needle hub with a needle having a needle tip extending from a distal end of the needle hub; a catheter tube attached to a catheter hub having a body comprising an interior surface defining an interior cavity, the needle extending through the catheter tube and the needle tip out a distal end of the catheter tube in a ready to use position; a valve positioned in the interior cavity of the catheter hub, said valve comprising an outer perimeter, at least one slit and two or more flaps; a valve opener sized and shaped to open the at least one slit to open the valve, said valve opener comprising a nose section (150, 430) having an activation end (166, 436) and a continuous perimeter section, two plunger elements each having two lengthwise edges, two stabilizer elements (253, 444) connecting the two plunger elements to form a stabilizing ring (255, 456), a holding space (155, 720) between the two plunger elements, a first through passage (61, 448) located between the nose section (150, 430) and the stabilizing ring (255, 456), and a second through passage (61, 448) located between the nose section (150, 430) and the stabilizing ring (255, 456); a needle guard comprising a resilient arm (288, 290) located at least in part inside the holding space (155, 720) of the valve opener, wherein said needle guard comprises an elbow i) projecting through the first through passage (61, 448), ii) projecting through the first through passage (61, 448) and in contact with a perimeter (65, 708) of the first through passage (61, 448), iii) projecting through the first through passage (61, 448) and in contact with the interior surface of the catheter hub, or iv) a combination of projecting through the first through passage (61, 448) and in contact with the perimeter (65, 708) of the first through passage (61, 448) and the interior surface of the catheter hub.