Weldcote 50/50 Tin/Lead Rosin Core Solder Contains A 2.30-3.20% Rosin Core. Rosin Core Solders Are Used In Applications Where You Are Soldering To Metals That Are Fiar To Excellent In Solderability: Coppers, Brass, Bronze Ad Nickels. With Some Exceptions, Tin-Lead Solders Can Be Used To Solder Copper And Most Copper Alloys, Lead, Nickel Alloys And Steel. The 50/50 Rosin Core Solder Is A General Purpose Solder Used For Non-Electrical Applications. It Is Used For Applicaions In The Sheet Metal, Stained Glass, Galvanized Gutters, And Radiator Repair Industries. The Tin-Lead Solders Are Not Recommended In High Stress Or Vibration Joints In The Cooling Industry Due To The Lack Of Sufficient Elongation Properties. This Product Contains Lead And Should Not Be Used In Potable Water Systems.