Urethane Flattening Agent is a universal flexible flattening (matting) additive for use in all Transtar urethane clearcoats and most competitive urethane clearcoat systems. It provides three different gloss levels with easy addition. Urethane Flattening Agent is easy to incorporate in the clearcoat, the activator or the activated clearcoat. TDS 702. Warning: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm.