Components

Small 5 V Dynamixel smart servo with a 77:1 gear ratio, fast and light, used for wrist and gripper joints.

Small 5 V Dynamixel smart servo with a 288:1 gear ratio, more torque for the main joints of low-cost arms.

12 V Dynamixel smart servo with a 250:1 gear ratio and a metal frame, the standard actuator of mid-size hobby arms.

Feetech STS3215 serial bus servo, 7.4 V with a 345:1 gear ratio, the actuator of the SO-ARM100 and its many forks.

Waveshare adapter that drives Dynamixel or Feetech bus servos from a USB port and passes power to the chain.

Idler wheel set that supports the far side of an XL430 joint so the servo horn is not the only bearing.