Luer connector including a primary Luer male connector, having a secondary female section extending from a top distal part of the primary Luer male connector back towards a proximal part thereof, the primary Luer male connector including a first inner fluid flow channel extending from a proximal end thereof to the secondary female section, the first inner fluid flow channel having a diameter of approximately d1 increasing at a connection point between the first inner fluid flow channel and the secondary female section to form a neck N the secondary female section having an internal diameter of d2 at a top distal part of the primary Luer male connector, where d1 is smaller than d2, the primary Luer male connector being configured to mate with a primary Luer female connector having a secondary male section including a second inner fluid flow channel ex having an internal diameter of approximately d1.