The phone holder is compatible with phones 2.3" to 3.34" (58 - 85 mm) wide and connects to the Super Convi Clamp base through the L Size (9") Dual Knuckle Arm. This arm is constructed by linking two S size arms with a 3" extension. The four ball heads of the arm allow users to adjust the mounted phones to precise positions that suit their special needs. The extension arm has three 1/4"-20 and two 3/8"-16 female thread holes that allow for mounting devices using an additional Super Knuckle Arm. The other end of the arm has a ball head with a hex stud that connects to the Super Convi Clamp. The Clamp can be securely mounted onto most rails or tubes with external diameters from 0.2 to 2 inches (5-51 mm). The included plastic saddle can be attached to the Super Convi Clamp to securely hold onto tables between 0.2-1.2" (5-30 mm) thick. The user-friendly clamp is easily secured and removed efficiently. This set mounts a phone within a flexible 9" (22.8 cm) radius.