Made of aluminum alloy, sturdy and durable, and can maintain stability in harsh environments without breaking like plastic products. Flexible knob for easy tightening. This is medium arm with total length of 3.5"(9cm). You can choose different lengths according to your needs. Compatible with RAM mounts and other all industry standard 1 inch(25 mm) B size adapters. This is a medium size arm, with total length of 3.5in(9cm) and net weight of 100g. It is made of aluminum alloy, sturdy and durable, and will not break like plastic products if used for a long time. The middle knob can easily tighten the arm. Compatible with RAM mounts and other all industry standard 1 inch(25 mm) B size adapters.High quality product is a good choice for you to install the mount on motorcycles, cars, bicycles, and ships.