Ordering mask online, medium or standard fit?

[chs8084]

I went to my local lds all set to buy that mask and after trying it out in the pool found it just did not fit without leaking.

 

[knotical]

I'm 5'7", 165lb with a medium face and I have the standard size as well!
... a good fit is almost a certainty. ...

I'm 5'10', 170 lb ( 1.77m, 77kg ) with a narrow face, not unlike yours, and it doesn't fit me.
If you can find a vendor with a permissive return policy, you could go for it. Otherwise, do whatever you need to find a mask with tempered glass that fits.