1. fixed valves are bridge like construction, extruded from the tray deck 2. these valves have larger vapour passage, 3. the trays operate at low pressure drops with higher capacities. 4. entrainment of liquid droplets is reduced appreciably. 5. the type of construction offers increased stiffness to the tray deck. no movement of valves and hence no wear and trays. 6. excellent fouling resistance