This is a seamless integration kit for a slide and hide Neff oven with a microwave/smaller 45cm oven installed on top of it. It covers the gaps between appliances for a better looking finish.
Brand new Neff product and never used. £50.
You can put your appliance number in here to check this will fit it.
https://www.neff-home.com/uk/shop-productlist/accessories/microwaves/microwave-ovens/installation/00773302#/Tabs=section-highlights/