If you are purchasing the same mask that you already have, then somewhere on your existing mask there will be a size indication, usually a single letter (M for medium, etc.). If you are feeling adventurous and purchasing a new style mask, then the best option is to call us and request a sizing gauge for the mask you are interested in. We have sizing gauges for many of the masks that we sell that we can send you at no cost. Please visit a local homecare dealer and see if they will be able to size you for a mask.
Items can be added to your purchase if the order has not yet been processed in the warehouse. Please contact Customer Service to find out if your order has shipped or if it remains open for new items to be added.