These are two brackets that can mount to the bottom of the Trekker to hold photo reflectors. Black and white contrast disks are included that can be read by sensors to allow the microcontroller calculate how far the robot has traveled.
This is a set of wheelchair motors and make great heavy duty robot motors. One left motor and one right motor. They are right angle gear drives with a release and electric brakes. They are 24VDC and the operating speed is 120 RPM.