A:Answer Jackie,
I am happy to help. It is going to depend as to whether you are installing this microwave over a wall oven, if so go by the exterior size of the wall oven. You can go with a 30 inch, which will go edge to edge on the cabinet. Both trim kits work with a cutout of 25-1/2" ± 1/8" wide and 16-3/4" ± 1/8" tall. I hope this helps. thank you for checking with us.