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.
