This Mouthpiece is designed for use with all TAP PAP Nasal Pillow CPAP/BiPAP Masks. The TAP PAP's mouthpiece is made of a soft, moldable polymer called ThermAcryl that is easily customized to provide an exceptionally stable and secure fit without pinching or pressure points. Once fitted the TAP PAP mouthpiece will not move or leak and does not require headgear; it fits snugly on your upper teeth without crowding the mouth or tongue.