Stadium BM725 127mm Core Drill Black Hole Ventilator
The benefits of "Black hole" Stops wind blasting in - The air flow within the duct is slowed down by the change of direction and by the vortices formed, reducing draughts to a minimum. Stops light showing through - The occupier cannot see through the ventilator and is less likely to be worried that insects and vermin may enter the house through it. 127mm (5") core drill "Black hole" ventilator. Tube length 228mm to 585mm with extension tube supplied. Fixed anti draft baffles 30cm free area.