The 1590Z166PL is an optional inner panel constructed from 16 gauge galvanized steel, intended for mounting components within the 1590Z166 series of watertight enclosures. This panel is sold separately and provides a sturdy, flat surface for securing electronic instruments and hardware inside the enclosure. It is designed to fit the 1590Z166, 1590Z166BK, and 1590Z166GY enclosures, which have external dimensions of 14.17 x 6.30 x 2.76 inches. Using this panel simplifies the assembly process by allowing for a clean, organized layout of internal components.