Kester 04-6337-0050 is Solid Ultrapure Bar Solder. This solder is comprised of SN63PB37 or, 63 percent tin and 37 percent lead. Please note, this item is sold by the box and has a 25 lb minimum.
Kester 04-3070-0000 is E-Bar Solder that is comprised of SN30PB70, or 30 percent tin and 70 percent lead.