Vertical/Straight Rotary Encoder 20imp/rotation (electronic brick)
A simple rotary encoder for all your projects.
It's like a potentiometer, but without end. It sends pulse to your microcontroller to let you know in which direction it turned. This version also has a button.
For more information on how to use an encoder, have a look at this good tutorial with arduino :
Actuator Length: 25mm
Detent torque: 3 to 20