Model SS-3M: Medium Duty
Model SS-3H: Heavy Duty
Every antenna system should have a spring. Springs proterct your antenna, your mount, and your vehicle. Firestik springs are made from top grade stainless steel and chrome-plated machine brass end pieces. They are made to last. The medium duty is for antennas up to 36" , and the heavy duty is for antennas up to 60". Fits all Firestik antennas, mount and accessories.