This connection assembly includes a tip defining a longitudinal axis and including a mounting area for mounting an adaptor thereon, and the adaptor including a mounting portion of thermoplastic material, forming a radial surface, which define a mounting opening for mounting the adaptor onto the tip. The mounting area includes at least one first portion having an outer surface which is located at a first distance from the longitudinal axis (A) and at least one second portion, adjacent to the first portion, having an outer surface which is located at a second distance from the longitudinal axis, the second distance being different from the first distance, the radial surface being located after assembly of the adaptor over the first portion and the second portion； The mounting opening and the at least one first portion and second portion are so dimensioned such that the radial surface of the mounting portion is in close contact with the outer surfaces of both the first portion and the second portion.
