Find Your Ideal Size: If the range from your left nostril to your right nostril is under 1.3 inches, please choose small size. In case of size selection errors, please don't hesitate to contact us. Your comfort and satisfaction are our utmost priorities Here we have several suggestions for you about the issues of fitting and air leakage. Firstly, please confirm that you have selected the most appropriate size according to the size chart. If you buy the wrong size, please contact us and we will send you the correct size. Secondly, if the nose bridge leaks, you can adjust the wearing position of the cushion. After the machine is turned on, wait for the cushion to inflate, gently pull the cushion away from the face and then stick it on, and manually sort out the silicone at the nose bridge. Thirdly, adjust the headgear to see if it can solve the leakage problem. If the headgear is too loose or tight, it may leak air. Fourthly, if there is air leakage between the frame and the cushion, please check whether the cushion is installed in place. Lastly, if the leakage can not be solved by adjusting the headgear or the size is appropriate, you can replace it with a different size.