From the Manufacturer
The Frigidaire MWTK27KF 27 “Microwave Trim Kit is compatible with many 27” Frigidaire countertop microwaves, but is model specific. It allows you to convert a countertop microwave into a built-in product. This trim kit frames out the cabinet space to give a finished, polished, built-in look. Frame is colored Black / Stainless. Frame material is plastic.