Provided is a drug delivery device including: a reservoir for a product, having a distally projecting end-piece defining an axial passageway for the transfer of the product, with a distal portion, an adaptor having a collar engageable around said end-piece said collar being axially movable with respect to said end-piece, securing structure for limiting the axial movement of said collar with respect to said end-piece, between a most distal position and a most proximal position of said collar, and biasing element for urging said collar towards its most distal position. An adaptor for forming a drug delivery device is also provided.
