The invention relates to an adaptor (10) for the distal tip (2) of a drug delivery device, comprising :- an inner ring (20) releasably engageable on said distal tip,- compressing means (30, 32), separate from said inner ring and intended to be snap-fitted onto said inner ring engaged on said distal tip by proximal movement of said compressing means with respect to said inner ring, said compressing means being capable of exerting a centripetal pressure on said inner ring so as to prevent axial movement of said inner ring with respect to said distal tip.
