Wrench size needed for SR-A10 extension shaft coupler? Shawn February 16, 2021 17:16 Updated You will need a 12mm wrench and a 14mm wrench. The picture below shows the proper placement of the wrenches. Related articles Common factors that cause high SWR readings Can I change the 10in shafts with a shorter shafts so I can put it on top of mirrors? Tuning Your Antenna for the Lowest SWR SR-955HPC Setup Guide Will the Antenna Tuning change if I'm using a 3" shock spring under the antenna ? Comments 0 comments Article is closed for comments.