Gates SCR Assemblies are specially designed and manufactured to convey Diesel Emission Fluid (DEF). Because DEF freezes at +11 Deg. F (-12 Deg. C), the hose and couplings are electronically heated using our revolutionary carbon-fiber heating system. This patent-pending technology allows for more uniform fluid heating compared to heated-wire designs and features thermoplastic over-molds to protect electrical connections against moisture and corrosion. SCR Assemblies use Diesel Emissions Fluid (DEF) as a means of converting NOx in engine exhausts into harmless diatomic nitrogen gas and water.