These terminals sre suitable for mechanical and natural (passive) ventilation installations. 5 to 25 Degree Pitch The pipework above the roofline is twin walled and incorporates an integral condensation drain. Specially designed for systems requiring a low resistance terminal, the Multivent Service Terminals are suitable for mechanical and natural (passive) ventilation installations. The pipework above the roofline is twin walled and incorporates an integral condensation drain. Two models are available, the UB34 with an internal diameter of 125mm and the UB35 with an internal diameter of 160mm. Special lower and higher pitch versions are available to order. The free vent areas of the units are 125mm dia 12,250mm2. 160mm dia 20,000mm2. The pressure airflow resistance of both units is