Accuracy engineered air capacity control valves with 90 degree adjustable handle ensures accurate airflows regulation and long lasting durability in HVAC systems. Features ABS construction for superior air tightness and tool without installation compatible for 75 to 200mm duct diameters. Essential for HVAC technicians, industrial maintenance crews, and enthusiasts upgrading ventilation efficiency in commercial or residential spaces. Optimizes airflows control in laboratories, hospitals, or coastal buildings requiring erosion resistant valves for humidity inclined environments. Manual butterfly valves design doubles as a stable check valves, maintaining directional airflows integrity across 20°C to +80°C operating temperatures.