Stadium BM701-3 Anti-Draught Black Hole® Airbrick Ventilator – 100cm² 27kW Double Brick Red Airbrick Stadium BM701-3 Black Hole® is an anti-draught black hole 100cm² Airbrick Ventilator for your Double Brick cavity wall. It has a telescopic cavity liner that can fit into a cavity wall thickness range of 230mm to 375mm. This airbrick also has a 27kw Net Rated input and a rectangular free area of 100cm². The airbrick will match your standard brick colour which is rust red. The black hole liner also blocks out most of the light coming in and greatly reduces the amount of outside noise you hear. The whole unit is supplied in four parts: a cavity liner with anti-draught baffles, an extension piece, an air-blast cowl and a white internal grill. This black hole airbrick is similar to our standard Double Brick airbrick but it includes a liner th