The MTC-14WG and MTC-16WG high humidity optional grilles address the weakest link when using ceiling speakers in high humidity applications, a steel grille that can rust. High humidity grilles extend the longevity of JBL's Control 10 Series model ceiling speakers - Control 12C/T, 12C/TBK, 14C/T, 14C/T-BK, 16C/T and 16C/TBK - (plus Control 26C and 26CT) when used in such applications. 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