A needle assembly (1) for mounting on an injection device is disclosed comprising: a main body (10) which is removably attached to an injection device in use； a needle (90) secured in the main body and having a forward portion which projects forwardly from the main body. The needle assembly further includes a shield (50) which is slideably mounted within the main body (10) and an actuator portion (70) which extends outside the main body and is configured for pushing the shield (50) forward manually in use. The shield (50) is slideably moveable between a first position in which the forward portion of the needle (90) projects forwardly of a shield cavity (64), and a second position in which said forward portion of the needle is located within the shield cavity (64). The shield (50) and main body (10) are provided with cooperating features comprising at least one latching element (66) provided on one of the shield (50) or the main body (10) and at least one corresponding engagement feature (44) provided on the other of the shield (50) and the main body. The latching element (66) moves into a latched position as the shield (50) moves into the second position to hold the shield in its second position.La présente invention concerne un ensemble d'aiguille (1) pour montage sur un dispositif d'injection comprenant : un corps principal (10) qui est fixé de façon amovible à un dispositif d'injection en utilisation ； une aiguille (90) fixée dans le corps principal ayant une partie avant qui fait saillie vers l'avant depuis le corps principal. L'ensemble d'aiguille comprend en outre une protection (50) qui est montée de façon coulissante à l'intérieur du corps principal (10) et une partie d'actionneur (70) qui s'étend à l'extérieur du corps principal est configurée pour pousser la protection (50) vers l'avant manuellement en utilisation. La protection (50) est déplaçable de façon coulissante entre une première position dans laquelle la partie avant de l'aiguille (90) fait sailli
