Another vote for Kester here. 24-6337-0027 is the part # for .031 diameter, "44" rosin core, 63/37 alloy 1lb. roll. I get mine from a place called gokimco.com, but it's usually not hard to find for 20-25.00 a roll if you google the part #. I've yet to find a solder I like better in my 25+ years as an electronic technician.