Gusmer GH-4 ProportionerThe GH 4 is engineered to be both simple and reliable. Gusmers point to point wired electrical cabinet sits atop Gracos industry proven hydraulic Reactor 2 chassis, including the Reactor horizontal pump line, fluid heaters, and hydraulic system. The Gusmer GH 4 hydraulic proportioner: a simple, durable machine offering impressive performance at an attractive price. Ideal for a wide range of spray foam applications, including roofing insulation,