Kester 24-6337-0001 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 "instantaction" 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.