There is some... discussion... about the Rotosound Tapes being flatwounds under the nylon outer shell (I've played them for many years, and I don't think they are); but, all the other tapes are light gauge rounds under the nylon. And, some of them are very light gauge, too. As far as actual, pounds-of-pull-to-pitch goes, there isn't a whole lot. OTOH, their stiffness? I've only used the medium scale Roto 88 Tapes, and a long scale, 5-string set of La Bella Black Tapes. Neither were what a reasonable person would call very flexible. However, there are all kinds of Tapes, from several different companies. So, I'd think that stiffness probably varies quite a bit, too. But, if you're looking for TI Jazz Flat flexibility? I think you'll be disappointed... You'll just have to decide if their tone and feel is worth a little stiffness. If not? Well... lots of other strings to try...