Anything can be held at customs. 50 vials? More than likely will get snagged unless your guy on the other end is stealth as fuck.
And they will look for sure. That’s too much glass not to look.
Legalities? Not sure. The stuff makes me sick as anything so I’ve never looked into it. Perhaps someone else can shed some light on it as maybe it can get by as s research chem. At best anticipate a wait, at worse... we’ll you know. However.... I’ve also seen customs do some strange and funny things.
Don’t take s risk you can afford to recover from though.