The type of housing depends on the ceiling material and insulation, and whether the lights are installed during new construction or a remodel. There also are specially designed housings to fit ceilings that angle up or down. Trim is largely a matter of personal taste and suitability with the décor.Downlights, as the name suggest, beam light straight downward, while eyeball-style fixtures pivot within their housing. Depending on where you want light focused, you can choose one, the other or a combination for your space. If you're installing them in a damp space, such as a bathroom, basement or covered outdoor living space, be sure you select models that are rated for moisture.