An injector includes an injector body having an upper portion defining a top surface. An injector core is received through the upper portion. The injector core has an interfacing surface that is disposed adjacent and raised with respect to the top surface. A cover member is disposed on the upper portion of the injector body. The cover member has a top wall disposed proximal to the top surface of the injector body and defining an aperture for receiving the injector core therethrough, a side wall extending from the top wall, and a lip that is disposed at an end of the side wall. The lip is adapted to be attached to a circumferential wall of the injector body through a snap-fit connection. Upon attachment, the top wall presses on the interfacing surface of the injector core to restrict an axial movement of the injector core relative to the injector body.