For my Rifles I have a single piece fiberglass rod, for my pistols a brass single piece rod.
I read the edge of the segmented rods create the perfect ridge to damage the bore, for that reason multi-segmented cleaning rods are not as good a single piece rod. Running my finger down a multi-segmented rod, I see their point, even good multi-segmented rods, that feel smooth between the segments, you can find a sharp edge here and there....
Yes, the cleaning rod bowing from the pressure can scrape the bore, and the greater the diameter of the rod, the stiffer it should be.... ...but I also don't want to carry multiple cleaning rods... ...and I have a .22 pistol and 5.56 AR, so my cleaning rods can fit a .22, thus a single piece fiberglass rod (with smooth sides) and for pistols a single piece cleaning rod, since its short enough bowing is not a concern, its cheap brass...