A high tech way to mark your dart throw line Adjustable line perfect for both soft and steel tip players Stays securely in place during game play Mounts directly into compatible electronic dartboards for a quick one-time setup Powered by the attached dartboard - no need to worry about batteries or cords Compatible with these Viper electronic dartboards: Solar Blast (model #42-1021), X-Treme (model #42-1022), 800 (model #42-1034), Orion (model #42-1036)