PROCOMM SSR50 4-1/2 INCH Bird Perch CB Antenna Mount Fits Volvo Trucks M8 Thread The ProComm SSR50 4- 1/2 INCH for Volvo series trucks replaces one of the M8 thread torque bolts on the mirror base to provide a metal to metal grounded solution for your antenna system needs. ProComm - Quality Products For Superior Communications. Features and Specifications:Mobile Antenna Mount4 1/2" Extra Long Mounting BarFor Volvo Series TrucksReplaces an Existing M8 Thread Torque Bolt on Mirror BaseStainless Steel BarChromed Brass FerruleKnurled Finish for Extra Grip