Add to Cart Compare Quick view DR21 Anti Draught Air Vent £36.00 The DR21 Anti-Draught Air Vent uses a 4”, 100mm hole which does not have to be drilled straight through a wall. A pilot hole can be drilled and then drill from each side. This has the advantages that a 100mm hole takes far less time to drill... £36.00 Add to Cart Compare Quick view