The aluminium sliding door is concealed in a wall cavitykey features sliding door is concealed when open"only suitable for new walls"double glazing option product description the aluminium cavity sliding door allows a 100% opening instead of the usual 50% and 66% opening of the normal sliding doors and stackers. This is great for optimising the available space inside any given room. The sliding door simply slides into the wall cavity leaving a fully unobstructed opening. Note: the aluminium cavity sliding door is only suitable for new walls.Technical details maximum panel height - 3000mmmaximum panel width - 1800mmmaximum overal width - 3600mmminimum cavity size - 50mm.