63/37 Tin/Lead 0.8mm Rosin Flux Core Solder Wire Reel 63/37 rosin core solder. FLUX 2.0%. wire diameter: 0.8mm. Melting point: 361F/183C. Good solderability, insulation resistance, No spattering and Non-corrosive. Widely used in electrical and electronics, solder parts like circuit board, electronics devices and others. Size : 5.5cm x 2.8cm.