+jonneil smyth It works well outside. As long as it is mounted properly. The purpose of grounding the unused ports is static buildup or noise from other ports and antennas. Some people notice tuning issues on non grounded multi port switches like this. Also gives it a direct ground in case of lightning strikes to unused antennas. otherwise they are at a floating potential.

Ham radio components are not cheap. Even MFJ or LDG is still pricey.