Fab5Freddy

Yes, I should have put that in original post. 100mm x 120mm external

Cheers @saveasteading

Cheers @saveasteading I just found these adaptors from square to round. It might help get a better seal, and cheap too. Various sizes. https://www.amazon.co.uk/Kair-Offset-Straight-Rectangular-Adaptor/dp/B004X4S1K0/ref=sr_1_30?keywords=cooker%2Bhood%2Bducting%2Bkit&qid=1696958221&sr=8-30&th=1

The thought just came to me I might be able to use a tapered dust hood from a wood working extractor - they end in round exit of roughly similar size? Then some tape on the joint Or....even better (cheaper) , a rain water/gutter hopper

@ProDave I've got a 3d printer but the bed wouldn't really be big enough for anything on this (I doubt) - but if any really inventive people come along later and can see such a possibility , then I'm open to it.

Cheers @ProDave. I can get inventive. So long as it's sealed , it'll be good enough? No real safety issues with a none standard vent? (I won't make it with plastic or cling film haha)

I can only seem to find round pipe for venting out of the cooker hood. Am I missing a part/adaptor from here to round for this? (photo is from above and sideways ) Can anybody point me to one please?