The problem with them and so many smaller players is that there isn't much proper independent third-party* group testing, without which you could be dosing up to 30% more than you think you are, or dosing nothing whatsoever (rare so far)
Second-party (vendor-commissioned) is fraught with fraud; now some vendors are starting to characterize their second-party tests as third-party, which they are NOT.
Barring group tests, you can pay ~$350 incl shipping to Central Europe, plus the cost of a vial, to do it individually.
* 1st party: the testing laboratory
* 2nd party: the vendor or manufacturing-process entity
* 3rd party: the consumer or independent organization on its behalf