Right On, I get that.
But I believe I've read that it takes a week, two, or a few until you get your BMT issued glasses and straps. I just got new glasses (and spent $300) and the last thing I want to do is have them fall off while exercising and either breaking them or getting them scratched.
I ordered these - Amazon Chums Glasses Retainers for when I go off to BMT. Based upon what I read with the various military service regulations, I think I'm safe with these for those first couple of weeks until I get my BMT BC (birth control) glasses. LOL
Yes, they work great. I use this: https://www.amazon.com/dp/B003CJSFHQ/ref=cm_sw_r_cp_api_eha1Ab822DAB9