Abstract: A microwave oven has an oven cavity with a wall (2) formed with a hole (6) covered on an external side of the wall by a metal launch box (8) and choke plate (7). A metal match plate (10) is mounted on the internal side of the wall (2) so that the match plate (10) and the launch box (8) form a launch cavity for delivering microwave energy to the cavity. The choke plate (7) has a peripheral choke channel which prevents leakage of microwave energy between the launch box (8) and choke plate (7), enabling the choke plate (7) and match plate (10) to be bolted to the wall (2).