Excellent tool for audio system test. Perfect for durably troubleshooting or testing car audio systems. You can use this phase meter to test car audio systems speakers, like subwoofer, door speaker and small treble and more.FeaturesColor: Black.Material: ABS, electronics.Size: About 11.00X7.00X2.50cm4.32X2.75X0.98in. Excellent for safely testing and troubleshooting audio systems, convenient for daily use. Can test all speakers in car, such as door speaker, subwoofer, small treble, and more. The low battery indicator lights up to indicate that the battery is low and is effectively used to test the polarity of the speakers. Unique fashion design, perfect replacement for old or damaged, extending service life and reducing maintenance costs. Designed and manufactured according to the original standard, easy to use, economical and practical.How to use: Play section 1 or 2, can check the leftright channel connection is right or not.Play section 3 or 4, the sound speaker will produce a fixed frequency signal.