This connection assembly (10) includes a tip (11) defining a longitudinal axis (A) and including a mounting area (21) for mounting an adaptor (13) thereon, and said adaptor (13) including a mounting portion (26) of thermoplastic material, forming a radial surface, which define a mounting opening (27) for mounting said adaptor (13) onto said tip (11). According to the invention: - said mounting area (21 ) includes at least one first portion (25 30) having an outer surface which is located at a first distance from said longitudinal axis (A) and at least one second portion (22), adjacent to said first portion (25 30), having an outer surface which is located at a second distance from said longitudinal axis (A), said second distance being different from said first distance, said radial surface being located after assembly of said adaptor over said first portion (25 30) and said second portion (22) - said mounting opening (27) and said at least one first portion (25 30) and second portion (22) are so dimensioned one with respect to the other that said radial surface of said mounting portion (26) is in close contact with the outer surfaces of both said first portion (25 30) and said second portion (22).
