MG Chemicals 63/37 Rosin Core Leaded Solder, 0.04" Diameter, 1 lb Spool, Meets J-STD-004 / J-STD-006 Non-corrosive and electrically non-conductive flux residue Standard Flux Core percentage at 2.2 percent Melting point 361 degree F 63 Percent tin, 37 percent lead, RA flux core