A fastening assembly having a tubular first coupling member; a second coupling member insertable coaxially inside the first coupling member in a first direction; and releasable fastening means for locking the first and second coupling member to each other in a predetermined axial lock position. The fastening means include: first and second engaging means formed on the first and second coupling member, connectable to each other to define a foolproof angular insertion/release position, and releasable by positioning the second coupling member in a predetermined axial position inside the first coupling member; and third and fourth engaging means formed on the first and second coupling member and connectable to each other in a further angular position of the second coupling member, different from the angular insertion/release position, by moving the second coupling member axially, from the predetermined axial position, in a second direction opposite the first direction.