The Wilson trucker version has a 5 or 10 inch shaft and my Sirio performer has an 8 inch shaft. But I am trying to find a 17-24 inch shaft. I don't know weather I am calling it the wrong name or weather 10 inch is the biggest you can buy. Want to mount the antenna in the stake hole in the bed of my pickup truck but have the coil at or above roof height. But do not want to drill though the roof, and getting ready to lay out 7,000 on a paint job so really don't want to use a mag mount.