A needleless syringe connector cap to be provided to a container having an aperture at its top, said cap comprising an elastically deformable plastic valve body. Said valve body comprises a first and second passage, each passage extending through the valve body. Both passages comprise a cross-slit valve in the extreme lower end of said passage, embodied as an aeration valve. The first passage is adapted to receive a first tapered syringe tip and the second passage is adapted to receive a second tapered syringe tip, wherein when fluid is withdrawn from a container to which the cap is provided through the first (second) passage using a first (second) tapered syringe tip to which said first (second) passage is adapted, the second (first) cross-slit valve opens in response to an under pressure in said container resulting from said withdrawal, so as to aerate said container.
