PQ12 series of actuators are the Original Actuonix Micro Linear Actuators. They all have the same stroke length but various gear, voltage, and control options
PQ12-P
Potentiometer position feedback, use with a compatible DC motor position controller to allow movement to any commanded position
PQ12-R
Internal Position Controller. Actuator will move to the commanded position. Compatible with RC Receivers, Arduino, and other Microcontroller systems
PQ12-S
Simple DC motor control. End of stroke limit switches automatically turn off motor when reached