Square Plate Polished Chrome. The Astra AST4003 narrow concealed door closer is a single spring hydraulic unit with easily adjustable closing speed. It is completely concealed when the door is closed, has a fixed size power EN 3 and a maximum opening angle of 105 degrees. The closer has been continuously tested to 500,000 cycles, tested to BS EN 1154 and fire tested to BS EN 1634-1:2000.. Alternative to face fixed closers. CE marked. Suitable for use on right and left swing doors. Fully concealed when door is closed