This device (1) for injection of a product into an injection site, the product being carried by a container (2) having an open proximal end and (2a) a substantially closed distal end (2b) coupled to a needle (4) to provide an outlet port for the product from the container (2), and a piston (5) provided in the container (2) and movable with respect to the container (2), the movement of the piston (5) causing the product to be expelled from the container (2) through the needle (4), said device (1) comprising: a housing (15) receiving at least partly said container (2), said container (2) being movable relative to said housing (15) between an initial position and a final position, said final position distally spaced relative to said initial position； a needle shield (6) releasably coupled with said container (2), for protecting said needle (4) prior to use of the device (1)； a safety shield (16) adapted to receive said container (2) and located at least partially within said housing (15)； and a deflectable longitudinal leg (13) which engages a proximal end of said needle shield (6) thereby preventing said container (2) from moving distally with respect to said housing (15) until a part of said needle shield (6) is removed from said container (2), a portion of the longitudinal leg (13) disposed between the needle shield (6) and the safety shield (16) in a stressed position, said longitudinal leg (13) deflectable from the stressed position, in which said longitudinal leg (13) prevents said container (2) from moving distally with respect to said housing (15), to a released position, in which said longitudinal leg (13) does not prevent said container (2) from moving distally with respect to said housing (15), wherein removal of said part of said needle shield (6) from said container (2) causing said longitudinal leg (13) to move from the stressed position to the released position.
