You are best to plug this product in and test before installing. This is to make sure you have the product facing the correct way for your set up. I had the product installed behind the unit hob in another unit on the island so I had to make some changes. The cut out wants to be just slightly bigger than the base measures to allow the screws and rivets to fit through. Make sure there is power close by as the unit plugs in to a normal socket. Also make sure there is plenty of room for the fan and control box. Operation wise it's pulls steam in from the closest hob cooking zones but fails to catch anything from the front. But I'm very impressed with its performance and features and it's not very noisy and best of all it's less than half the price of its competitors.