Kester 331 Rosin Core Solder 63/37 .031" 1 lb. Spool Kester 331 is a water soluble formula flux-cored solder wire. More heat stable than most organic fluxes, using this solder wire results in minimal smoke and odor, and can be removed with a water rinse. Kester 331 organic flux is more effective than rosin fluxes when soldering difficult metals such as copper, nickel and brass. High heat stability allows for minimal smoke and odor. NOTE: Extremely active. Residues may need to be removed ater soldering.Kester 24-6337-6403 Features:Wire diameter: .031 is most common for electronics work" Alloy: Sn63Pb37 (63% Tin / 37% Lead)Melting range: 361°F (183°C)Core flux type: Water SoluableCore size: 66Spool size: 1 lb.Factory fresh, not used or surplus materialShelf life: 3 years from DOMRoHS compliant: NoA few warnings and cautions:For industrial use onlyWe can not offer advice on a specific application. For use by experienced electronics technicians User assumes all risk for application.Any warranties are limited to replacement or refund of product.Always wear safety glasses when working with soldering equipment and materials Always use adequate ventilation when working with soldering equipment and materials Avoid breathing flux fumes emitted during soldering.Flux fumes may cause pulmonary irritation or damage.This product may contain chemicals known to the state of California to cause cancer and/or other reproductive harm.