Mast is Oooooold School, I wrote a piece on it once.

Pre-dating Winny and Var, it has fallen out of vogue since their inception largely because of their oral availability and much shorter half-lives. But it always had a great reputation for definition results, was considered a good buy for the amateur bb’er, highly effective at about 500mgs a week, and AR spoke highly of his experience with it in the Mast profile.

It’s more comparable to Winny, in that one-trick pony respect, and therefore inferior to the comprehensiveness of Var which is of course more expensive too.