A system for transferring medical fluid includes a male Luer connector and a female Luer connector, the male Luer connector including a collar surrounding at least part of a male conical portion whose outer surface is supported against the female conical connection surface of the female Luer connector during the assembly of the connectors. The maximum inside diameter at the entrance to the collar of the male Luer connector is strictly less than the smallest outside diameter of a standard female Luer connector or one according to ISO 594-2. The female Luer connector includes a collar surrounding at least part of the female conical connection, this collar having an inside diameter greater than or equal to the outside diameter of the collar of the male Luer connector, to engage and at least partially cover the collar of this male Luer connector during the assembly of the connectors.
