The standard ball head included with the product has a diameter of Φ17mm. If you wish to mount the device on a 1" (25.4mm) mounting bracket or arm, please purchase the 1" RAM Ball Head accessory and replace the standard ball head with it.
Use 1″ RAM Ball Mount: Requirements
The standard ball head is 17 mm; to use a 1-inch (25.4 mm) RAM mount, swap in the 1-inch RAM ball head accessory.