The Mirage Activa LT combines the original Activa's superior sealing technology with a lighter, quieter, and more streamlined design. The Activa LT's ActiveCell cushion expands and contracts to creat a comfortable, unwavering seal as you move and turn during the night. The MicroFit dial makes fitting quicker and easier than ever before and the innovative diffuse vent design means that the Activa LT is approximately 49% quieter than the original!