This investigation is designed to evaluate the performance (leak and comfort) as well as the participant's overall acceptance of the trial nasal mask amongst Obstructive Sleep Apnea (OSA) participants. An important factor in this investigation will be the testing of two different seal sizes on the participants (medium and large size). A total number of 12 participants who currently use nasal or nasal pillow masks will be recruited for the trial. Participants have been selected based on their anthropometric measurements collected in previous trials (CIA-103). Participants from previous NZ trials may be recruited into this trial with their consent. All the participants will be recruited from the Fisher & Paykel Healthcare Database of subjects with OSA (Ethics Reference NTY/08/06/064), Auckland District Health Board (ADHB) and New Zealand Respiratory and Sleep Institute (NZRSI).