I would recommend you buy a mask only after you try it in water with a snorkel or regulator in your mouth.........
Let me explain why........on our recent family dive trip to Maui, my darling wife's prized Aqualung Mythos mask was broken.......a weight fell on it and shattered one of the lenses.
We went to a store and bought her a new mask (incidentally a Mares Liquid Fit) it passed the classic in-store fit test with flying colors.......
Step 1 - Lean head back looking up.
Step 2 - Pull all hair out of the way, hair will make any mask leak
Step 3 - Inhale though you nose and hold your breath do not push the mask on, it should "suck" to you face
Step 4 - Look down and into a mirror, if the mask stays and seals air it should seal water
Step 5 - put a mouth piece in your mount and repeat
She got in the water the next day and it leaked, so much in fact that on the second dive she took my prized black skirt Mythos mask (and she really hates those black skirts) and thrust the Liquid Fit at me with only a grunt.........I was after all the one who dropped the weight on her beloved mask.......
I was OK with that as I "never" have mask problems, and have dove with all kinds of no-name, half broken, rental masks around the world......well it leaked on me too, it just would not seal......
Finally, I traded with my son and he got a decent seal with the mask.....not saying that anything is wrong with the Liquid Fit mask, just that "fit" is everything with a mask......
Hope this helps........M
PS we are a family of 4 divers age 13 to 43 and we all use the same Mythos mask.......I mean not the "same" mask.....we have 4 in different color/skirt combinations so we can tell them apart.......strange, I know but true....