It is long defunct but a well respected UG lab in the early 90s would sell you 100 ml jugs of 400 mg per ml test cyp. It was really good stuff

Prob was the stopper would start to get so many holes in it that one would have to filter the gear as there were little orange bits of stopper in the oil.

20 ml makes sense though.

I suppose the more you draw from a vial the more chance you have of contamination? just a hypothesis.