Kair Rectangular Ducting 180mm X 90mm - Airbrick With Damper. Fits inside Kair Rectangular Plastic Flat Ducting 180mm x 90mm. Part: DUCVKC651. The backdraught shutter stops unpleasant odours, noises, or draughts flowing back through your duct. Depth of rear spigot: 60mm. For use with 180mm X 90mm duct. Can be used for whole house ventilation, passive stack vent, air conditioning, HVAC, and Heat Recovery Systems. Easy installation. Maximum/Minimum Temperature: +60c / -15c. Weight: 0.26 Pounds.