The current black cast base is made specifically for the 67 Design's metal BL20 20mm ball mount. The base is sold with at least one carbon fiber arm.
After that you can certainly put whatever device holder you wish. We support many manufacturer's device holders that have a 0.75", 20mm or 1" ball mount.
To mount a 1" ball on the carbon fiver arm, you will need to purchase a Dam Adapter™.