Techspray uses 2 types of flux: Prowick line is a natural gum rosin. Per J-STD-004 Section 3.2, the Prowick is classified as ROL0. Per British Std. EN 29454-1:1993 and ISO9454-1:1990, Prowick has a classification of 1.1.1.B. No-Clean flux is a synthetic (non-colophony)flux. Per J-STD-004 Section 3.2, it is classified as REL0. Per British Std. EN 29454-1:1993 and ISO9454-1:1990, the No-Clean flux has a classification of 1.2.3.B.