Electrolux RSTO and RST unitary electric immersion systems provide low-watt density heating for viscous materials such as asphalt, fuel oil, pitch and tar, liquid sugar, molasses, lube oils, linseed oil, and other heat-sensitive materials. They can be installed in above-ground tanks and in below-ground tanks with access to one tank end. Model RSTO systems are recommended for cramped locations and the RST model features metal-sheathed heating elements in place of the open coil elements.