UNI-MAG Mounting Plate for Aluma Duty Trucks and RV's provides a magnetic surface for vehicles with alloy, plastic, or fiberglass roofs. An excellent companion for the UNI-MAG antenna mount. A strong 3M adhesive helps affix the plate to almost any surface, facilitating the mounting of your UNI-MAG antenna mount. The plate measures 5-1/4in wide.