K0150 22 Connector Coupler Connection Hose with Backflow Valve/Round Air Tube Diameter 150 mm Ventilation System Channel

Its a back draft preventer. It is fully functional but a tendency to 'clunk' when the wind is causing a through draft... (I will find a way of fixing this)It wasn't supplied in a tin but does everything its supposed to..

Works great, and easy to install. It does create a tapping noise from the bathroom fan as draughts slightly open the vent and it falls closed again; there's no soft stopper. Easy enough to fix with a little bit of foam.

Work just fine, use it in our summer house outside

Does the job when installed.

Prevents drought when wind blowing in certain direction