A counter weight door has a plurality of counter weights each associated with a respective one of the panels and an interconnecting spring connecting each of the weights to the next. At least one of the counter weights has a cradle which is arranged to receive a plurality of weighted members. The spring arrangement connecting one counter to the next is housed within the cradle and includes a shaft on which the spring is mounted. The door has a pulley system which has a first pulley on one side of the door, a second double pulley on the other side of the door, a first cable fixed at a first end to the door extending through the first pulley and a second cable fixed at a first end to the door extending through the second pulley to the counter weight system.