Headgear for F40 - How to Determine Correct Size

[WearyOne]

Any suggestions on how to determine the correct headgear size for the Resmed Airfit F40? They come in different sizes because they do not have any adjustment on the top of the head. If this helps at all, I always have to adjust the headgear tighter for any other mask I've had. I determined the mask seal size with their template (medium), but can't figure out if my headgear should be small or medium (I know large wouldn't work). I know I can return it with cpap.com if it doesn't fit, but I would just like to avoid the hassle of doing that if possible. Thanks for any suggestions.

[yonchee1]

I also use the F40i, headgear is one of those things where trial and error seems to prevail. My hat size is 7 and 3/8, I use the small headgear and it feels comfortable
thru-out the night. Originally, I was using the large mask, but found the medium mask sealed better and has less leaks. I was using the F20i mask but watched the
reviews for the F40i, I changed immediately when my next auto shipment was sent out. I have experimented with the F20i headgear with the F40i mask, it is
a good backup but not perfect when it comes to fit and function. One of the things I did to my F40i headgear is I sewed the bottom straps in the position that
seals the best and does not put too much pressure on my face. The Velcro seems to be the weak link, after normal use of about 2-3 months the Velcro looses
its ability to hold. I hope this helps with your decision.