Hi! Although the general service was very good, unfortunately the holes in the medium nasal CPAP mask liners (K11-NM) I ordered are far too big and keep slipping from under the mask and into my mouth. Therefore the seal on the mask is broken and I am not getting the benefit from my CPAP machine. I am using the grey Swift FX Nano so thought that the medium liners would be the obvious choice of fit. However,this is not the case and a small size would probably have been more suitable as they seem to come up quite large. I have only used three of the liners so it turned out to be quite an expensive exercise. M. Hughes