A device for injection of a product into an injection site, the product being carried by a container having an open proximal end and a substantially closed distal end coupled to a needle to provide an outlet port for the product from the container, and a piston provided in the container and movable with respect to the container, the movement of the piston causing the product to be expelled from the container through the needle, said device comprising: a housing receiving at least partly said container, said container being movable relative to said housing between an initial position, in which a tip of the needle does not extend beyond a distal end of said housing, and a final position, said final position distally spaced relative to said initial position, and in which the tip of the needle extends beyond said distal end of said housing; a needle shield releasably coupled with said container, for protecting said needle prior to use of the device; a safety shield adapted to receive said container and located at least partially within said housing; and a deflectable longitudinal leg which is in contact with a pushing surface of the needle shield prior to removal of said needle shield from said container, said pushing surface thereby forcing said longitudinal leg in a stressed position prior to removal of the needle shield, a distal end of the longitudinal leg being located between said pushing surface and the safety shield, said longitudinal leg deflectable from the stressed position, in which said longitudinal leg prevents said container from moving distally with respect to said housing, to a released position, in which said longitudinal leg does not prevent said container from moving distally with respect to said housing, wherein removal of said needle shield from said container causes said longitudinal leg to move from the stressed position to the released position, wherein said longitudinal leg comprises a peg, and wherein said peg engages a recess located on the safety shield when said longitudinal leg is in the stressed position and said peg disengages said recess when said longitudinal leg is in the released position. a housing receiving at least partly said container, said container being movable relative to said housing between an initial position, in which a tip of the needle does not extend beyond a distal end of said housing, and a final position, said final position distally spaced relative to said initial position, and in which the tip of the needle extends beyond said distal end of said housing; a needle shield releasably coupled with said container, for protecting said needle prior to use of the device; a safety shield adapted to receive said container and located at least partially within said housing; and a deflectable longitudinal leg which is in contact with a pushing surface of the needle shield prior to removal of said needle shield from said container, said pushing surface thereby forcing said longitudinal leg in a stressed position prior to removal of the needle shield, a distal end of the longitudinal leg being located between said pushing surface and the safety shield, said longitudinal leg deflectable from the stressed position, in which said longitudinal leg prevents said container from moving distally with respect to said housing, to a released position, in which said longitudinal leg does not prevent said container from moving distally with respect to said housing, wherein removal of said needle shield from said container causes said longitudinal leg to move from the stressed position to the released position, wherein said longitudinal leg comprises a peg, and wherein said peg engages a recess located on the safety shield when said longitudinal leg is in the stressed position and said peg disengages said recess when said longitudinal leg is in the released position.