The HS-422 has been around for a while and for a good reason, durability and the ability to be easily modified. For inexpensive robotic applications this the perfect servo. It can easily be modified for wheeled applications since the output shaft is supported on the botton and top with bronze bushings and the potentiometer is indirect drive. The circuit board is also seperate from the motor so the potentiometer can be easily accessed. Simply a great servo at a great price.