This is a robotic mouse that uses opto interrupters to see the world. It follows black lines on a table or other surface no matter how it twists and turns. When the line runs out, the mouse stops. Soldering required. Includes detailed instructions. Features: Programmed IC * Microphone * Photo Interrupters * Gearboxes. Requires: Four (4) AA batteries (not included.) See the Components: Batterries section for great deals on batteries! 1 Each Line Tracking Mouse RASELTM$34.99 Copyright © 2003-2009 E-Clec-Tech. All rights reserved. All other materials and logos are copyrighted by their respective owners, or companies.