Kester's 44 rosin flux is an activated rosin formula for use in flux-cored solder wire. 44 has virtually dominated the field of activated rosin core solders for well over five decades. An outstanding performance feature of this flux is the “instant-action” wetting behavior. The high mobility and fast-spreading action of this flux results in more reliable production line soldering. Under IPC J-STD-004, 44 is classified as ROM1. Despite the increased activity and soldering performance, 44 passes both 85°C/85% RH and 40°C/90% RH SIR test methods.