The interior of each Vicair® Liberty cushion is equipped with a valve which regulates the amount of 'free air' between the cells. When using the cushion for the first time, the valve is opened for a while, allowing the amount of free air to be automatically adjusted to the user's weight and body contours. After following this procedure, the cushion is ready for long-term and problem-free use. All Liberty cushions are available with two types of outer cover, Comfair and Incontinence. The top fabric of both covers is stretchable in two directions, guaranteeing optimal immersion of the body into the cushion. The Comfair cover has a breathable top fabric for comfort and moisture dispersal. The Incontinence cover is made of a vapour-permeable, waterproof material.