BotBrain robotics line sensor. Compatible with BotBrain robotics kits. Three sensors which detect changes from dark to light surfaces allow your robot can do precise, accurate line following. Use two or three for Line Following. Use a pair to build wheel encoders. Detect edges or surface color changes in the robot firefighting, planetary exploration or grand challenges. Range: 1-10-millimeters. (1/16 to 1/2-inches). Each sensor requires two inputs on BotBrain Board. Through the hands-on learning experience offered by BotBrain, robots help students transform abstract science, technology, engineering and math (stem) concepts into concrete real-world understanding with teacher-written and classroom-tested curricula. Grade level: middle-high school. No allergens. Warning: choking hazard-Small Parts, Not for children under 3 years.