HN-504 is the heart of the OS TECH Direct Plating System. It provides the constituents that render nonconductive surfaces conductive. HN-504 is packaged as a two-component system. HN-504A Carrier is the aqueous stabilizer solution and HN-504B Catalyst is the precious metal-containing suspension. When HN-504B is mixed with HN-504A they form the HN-504 activator bath.