APC38AMPS is a circular 38mm ball to 4-Hole AMPS adapter that is compatible with 38mm (1.5 inch) mounts and pedestals, including Arkon Mounts' 38mm double-ball compatible mount shafts, RAM Mounts Size C double socket arms, or other third-party 38mm ball compatible components. (Mounts, holders, and devices sold separately.) The adapter's construction provides a sturdy connection for drilling into dashboards or other solid, flat surfaces, and is ideal for commercial or fleet use. APC38AMPS measures 2.49 inches in diameter with a circular design that is a great alternative for locations where a square adapter won't work.