The ‘x’ in SunTour Vx S was widely understood as standing for ‘extra light’ (I do not know whether this was SunTour’s real intention). This was the SunTour V T Luxe after it had been on a strenuous diet, the steel holder for the cable clamp bolt has been replaced by an aluminium channel and the knuckles are slimmer and neater.
Despite the weight loss, this was an extremely affordable, strong and reliable derailleur - I still see many of these in use on the roads today.
This example is of one of two variations on the theme of a mid length cage derailleur in the Vx series (the other being the first style of Vx). This is the commoner and more typically SunTour variation that does have a Quick Cage (unlike the Vx).
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