An injection apparatus for injecting eggs of varying sizes and different orientations in an incubating tray that includes a substantially horizontal support plate with vertical openings therethrough, and vertical injectors resting in the openings and able to slide therein with respect to the plate such that the injectors can move vertically in the openings while remaining engaged with the support plate so as to maintain their vertical orientation throughout an injection sequence. For each opening, an expandable ring is positioned in the plate and pneumatically expanded to tighten around its respective injector after the injector has adjusted vertically in its respective opening to the height of an associated egg in order to maintain the injectors in their vertical orientation for injection of their associated eggs.