All masks can be purchased over the internet Save $$$ on Resmed regular prices and $$$ on Fisher & Paykel prices over the net. Go to our web store to order Masks are compatible with most machines but do need to be fitted by a professional technician. If buying over the internet it is best to stick to what you know. ie stick with the brand and size that you already have. Masks purchased over the net are NON refundable.