Beers Technic Tennis Computer ERT 300 is the only microprocessor worldwide for precise determination of string tension and playing characteristics of any tennis racquet. The technology of world class players from the number one innovator in racquet diagnostic systems, allows specialist tennis retailers, coaches and stringers to find the optimum tension and performance of any frame. This is the perfect device to determine your optimum racquet stringing, ensure that your tournament racquets have the same DT (stiffness of the string bed) and therefore identical playing properties, reliably determine when your racquet needs to be restrung so that you can continue to build on your high level of performance and enjoy playing tennis without arm and back complaints. As you will know best, you need to be able to trust your own equipment on the court. It is only when you are sure that you have the perfect tools that your head is clear to think about the big points and that you can concentrate fully on your opponent and the game. Enjoy your victories! The ERT 300 comes in a soft case of high quality, manual in 4 languages; English, German, French and Italian, DT-System-Disc (Tension Advisor) and 2 batteries (CR 2032 coin type).