<p>A cap (2) suitable for use with a PET beverage bottle has an integral gas barrier provided by a plastics-coated aluminium foil disc (30) having its peripheral edge (32) embedded into the plastics internal or external surface (40) of a top panel (4) of the cap or of a valve (20). A plastics component (28) from which the cap (2) can be produced is described. The component (28) has a recess (48) defined by a sacrificial wall (50) formed inwardly of a resealing valve (20).</p>
