2017 and newer Freightliner Cascadia P4 mirror base antenna mount with JBC910H SO239 stud fits 3/8" x 24 thread standard CB antenna. Adjustable forward angle design reduces reflections from the cab for optimal performance from all antenna designs. Heavy-duty design can hold larger antennas. Works on either driver or passenger side. Made with 5-gauge heavy-duty aircraft-quality aluminum. Stainless steel hardware included.