SparkFun TOL-09161 Solder Leaded – 100-gram Spool
This is your basic spool of leaded solder with a 63/37 water soluble resin core. 0.031″ gauge and 100 grams. This is a good spool for more advanced users that should last 6-12 months depending on how often you solder.
Mix: 63% Sn / 37% Pb