The APCMAMPS38 38mm ball to 4-Hole AMPS circular metal adapter is compatible with 38mm (1.5 inch) mounts and pedestals, including those from Arkon or RAM Mounts. (Mounts, holders, and devices sold separately.) The adapter's metal construction provides a sturdy connection for drilling into dashboards or other solid, flat surfaces, ideal for commercial or fleet use. The circular design is a great alternative for locations where a square adapter won't work.