Slot Size: 340x12. Technical Data EA to BS13141-1: 2830.
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It provides automatic ventilation and sound insulation for use near noise sources. Energy saving, reduces over ventilating.
eBay
Get this deal while you can I got this from a clear out at work these are verry high quality you don't find them any cheaper elsewhere external Acoustic trickle vent in black and anthracite gray 17x1.5-inch Made from aluminium designed to provide a practical and stylish addition to your home. these vents are designed to reduce noise from windows facing roadways and improve air circulation and quality Ideal for DIY enthusiasts looking to upgrade their home windows with a practical and modern solution. Packaging is roughed up a little but the contents are perfectly fine, internal vents are sold separately so you get a choice of what colour suits your decor
eBay
Slot Size: 340x12. Technical Data EA to BS13141-1: 2830.
eBay