I conceived of Concedo strings at least thirty years ago or more, because I noticed that the dyed strings did not break when tying a knot, they were more flexible than the natural strings. I suggested this back then, and when they began making them, I wasn’t notified, so I’ve never tried them. I am now using Bow Brand heavy-gauge gut strings and love them. They’re not actually heavy, they’re the original gauging before they were thinned back in the ’90s.