The SunTour Mountech was SunTour's attempt to incorporate Huret's double-parallelogram ("Duopar") design into a slant-parallelogram derailleur without stepping on Huret's patents. As noted above, it shifts beautifully but is intolerant of debris in the upper pulley assembly. This was problematic for its initial intended market as a mountain bike derailleur.

If you have one, keep it clean and it should serve you well.