5 ply load range C ST tire?

Plys are a old way of measuring the strength of a tire. With todays advanced materials, it takes few plys to achieve the same or greater strength, hence the newer "ply rating" system. Few if any tires actually use the number of plys that the "ply rating" says.

In fact fewer high quality plys may well be better that more low quality plys.... The hard part can be separating the truth from marketing.