SIBOASI S3015 is a beginner-level model tennis ball shooter machine. Remote controlled. Directly use AC power (110V or 220V), an external battery which lasts 3-5 hours is available for option. Image you can keep the machine in your car or first floor and take away the external battery to charge for next practice. You are able to customize your drill adjusting serving interval, speed, height. Preset drills are full random, fixed point, deep-light ball circullation, two line, three line, 6 kinds of cross line and overhead smash drill.