Knockout couplers, for injection machines with hydraulic or mechanical ejection, are ideal for use with quick mould change systems & also two stage ejection. They provide a quick and easy method (even on existing moulds) of attaching the ejector plate in the mould to the ejection system in the moulding machine. Provides positive assured ejector plate return while greatly reducing set up time. Ideal where the ejector plate is difficult to reach or when centre ejector is desired but impossible to "tie-in"