The MTC-16WG grilles address the weak link when using ceiling speakers in humidity applications, a steel grille that can rust. These grilles extend the longevity of JBL's ceiling speakers. The aluminum alloy material does not rust and the durable powder-coated finish prevents pitting that could otherwise occur with raw unfinished aluminum. The finish provides a nice look that matches with the speaker. To use the grille, simply install onto the speaker instead of the grille that comes with the speaker.