Marlin P. Jones and Assoc. Inc. has a few types of Multicore solder at reasonable prices. www.mpja.com Stock numbers 15342-TL; 15341-TL; 15345-TL; 15344-TL; 15346-TL. To the best of my knowledge (thanks to N0SS) WRAP3 flux is standard rosin core, and X38B flux is a no clean similar to the current Crystal 400. 72 Joe, w4jhr