I've been exploring alternatives to the conventional wound 4th, which I've never been particularly satisfied with. I can now report that the "KF Alliance" fluorocarbon strings offered by Savarez do well in this regard. As singles, they're sold in 1m and 2m lengths, marketed for harp and early instruments. I'm using .0291", although I might try the next higher gauge (.0303") at some point. Very clear/responsive at all dynamic levels, stable, and it seems like they last a long time (fingers crossed). Not at all like those awful Nylgut unwound 4ths (do they even still make those?). I don't think I'd ever go for an all-fluorocarbon set, as I'm pretty happy with LaBella's. To my ear, the fluorocarbon 4th sounds more timbrally balanced against the nylons, which may or may not be desirable (if you like that the wound 4th has a distinct voice). Well, just thought I'd share.