Kester 04-6040-0050 BAR, SN60PB40 is Ultrapure Leaded Bar Solder.  60 percent Tin and 50 percent Lead. Sold per bar.

• This solder is made by a special process which controls the inclusion of oxides and metallic and non-metallic impurities, Kester Ultrapure is the industry standard bar solder for use in high tech electronics applications where lower surface tension and hole filling ability are essential.
• The purity of Kester Ultrapure far exceeds the requirements of QQ-S- 571-F, ASTM B32, and ANSI/J-STD-006.
• All Kester bar solders are made from Grade A virgin metals and manufactured under a controlled process to produce a high purity, uniformly alloyed bar solder.
• Quality requirements are much stricter than military and ASTM specifications to meet the needs of today's automated electronics soldering operations. Impurities such as copper, cadmium, zinc, aluminum and iron are at a minimum.
• The manufacturing process also minimizes metallic oxides and virtually eliminates sulfur, non-metallic inclusions, and other possible contaminants.