This Connector is only used for the Philips Respironics DreamWisp Nasal CPAP Mask. The Connector is used to attach the top side sections of the frame at the top of the head and will also increase or decrease the length of the frame. Although 90% of cpap users will find the medium size connector the best fit, sizes small and large are also available. If the mask frame falls backward and is too close to your ears, you may need a smaller size connector. If the frame falls forward on the head and is too close to your eyes, you may need a larger size connector.