https://www.dfrobot.com/product-823.html
This encoder is matched with 2wd miniQ Robot chassis. AB two-phase pulse wave,measured by two infrared reflective sensor.
robot chassisminiqencoderdfrobot
https://www.dfrobot.com/product-827.html
This MiniQ motor wheel set is especially designed for education and hobbies. It features a powerful metal gear motors which provide a speedy robot.
motor wheelminiqsetencoderdfrobot